Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Effect of bean structure on microbiota utilization of plant nutrients : An in-vitro study using the simulator of the human intestinal microbial ecosystem (SHIME®)
    Rovalino-Córdova, Ana M. ; Fogliano, Vincenzo ; Capuano, Edoardo - \ 2020
    Journal of Functional Foods 73 (2020). - ISSN 1756-4646
    Fermentation - Food structure - Red kidney beans - SHIME® - Starch

    Colonic fermentation of resistant starch provides health benefits to the host. However, physical characteristics of the food matrix could limit the availability of starch and other dietary fibres for microbiota utilization. In this study, the influence of food structural aspects was studied by using cotyledon cells from red kidney beans with different levels of cellular integrity. In-vitro colonic fermentation was conducted in the simulator of the human intestinal microbial ecosystem (SHIME®) where the utilization of starch and other non-starch polysaccharides was investigated along the three colon regions. Results indicate that plant cell integrity modulates nutrient utilization by gut microbiota where higher amounts of starch were delivered to distal regions of the colon in intact samples. Other dietary fibre constituents, such as pectin, were also differentially fermented depending on the level of cellular integrity. Moreover, bean supplementation produced changes in microbiota population favouring the proliferation of Bifidobacterium species.

    How processing methods affect the microbial community composition in a cereal-based fermented beverage
    Phiri, Sydney ; Schoustra, Sijmen E. ; Heuvel, Joost van den; Smid, Eddy J. ; Shindano, John ; Linnemann, Anita R. - \ 2020
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 128 (2020). - ISSN 0023-6438
    Bacterial community - Fermentation - Munkoyo - Rhynchosia - Zambia

    Traditionally fermented beverages significantly contribute to food security in Africa. The nutritional and sensory quality characteristics of these beverages are closely linked to the different microorganisms they contain. We studied the effect of processing methods on the microbial composition of Munkoyo, a cereal-based fermented beverage, in three Zambian agroecological zones. In Choma, porridge was made from maize grits to which a watery extract from Rhynchosia roots was added as a source of enzymes. In Nyimba, maize meal was used to make porridge, in which Rhynchosia roots were submerged overnight. In Kitwe, porridge from maize meal was cooked until caramelization, followed by submersion of Rhynchosia roots. Irrespective of processing method, final pH was 2.5–3.5, with the lowest value for Nyimba. Presence and abundance of 16S rRNA encoding DNA sequences of the microorganisms showed no clear clustering on basis of the processing method but significantly affected the operational taxonomic unit (OTU) composition (anosim, R3,13 = 0.407, p < 0.05). The average Shannon indices, which indicate ecological diversity, were: Choma 1.14 ± 0.64, Nyimba 1.58 ± 0.23, and Kitwe 1.07 ± 0.95. Consequently, for industrial upscaling and quality standardization, specific combinations of different bacterial species can produce Munkoyo that addresses local consumer preferences.

    Multilevel optimisation of anaerobic ethyl acetate production in engineered Escherichia coli
    Bohnenkamp, Anna C. ; Kruis, Aleksander J. ; Mars, Astrid E. ; Wijffels, Rene H. ; Oost, John Van Der; Kengen, Servé W.M. ; Weusthuis, Ruud A. - \ 2020
    Biotechnology for Biofuels 13 (2020)1. - ISSN 1754-6834
    Alcohol acetyl transferase (AAT) - Anaerobic - Bioreactor - Eat1 - Escherichia coli - Ethyl acetate - Fermentation

    Background: Ethyl acetate is a widely used industrial solvent that is currently produced by chemical conversions from fossil resources. Several yeast species are able to convert sugars to ethyl acetate under aerobic conditions. However, performing ethyl acetate synthesis anaerobically may result in enhanced production efficiency, making the process economically more viable. Results: We engineered an E. coli strain that is able to convert glucose to ethyl acetate as the main fermentation product under anaerobic conditions. The key enzyme of the pathway is an alcohol acetyltransferase (AAT) that catalyses the formation of ethyl acetate from acetyl-CoA and ethanol. To select a suitable AAT, the ethyl acetate-forming capacities of Atf1 from Saccharomyces cerevisiae, Eat1 from Kluyveromyces marxianus and Eat1 from Wickerhamomyces anomalus were compared. Heterologous expression of the AAT-encoding genes under control of the inducible LacI/T7 and XylS/Pm promoters allowed optimisation of their expression levels. Conclusion: Engineering efforts on protein and fermentation level resulted in an E. coli strain that anaerobically produced 42.8 mM (3.8 g/L) ethyl acetate from glucose with an unprecedented efficiency, i.e. 0.48 C-mol/C-mol or 72% of the maximum pathway yield.

    Enzymatic hydrolysis of pea protein: Interactions and protein fractions involved in fermentation induced gels and their influence on rheological properties
    Klost, M. ; Giménez-Ribes, G. ; Drusch, S. - \ 2020
    Food Hydrocolloids 105 (2020). - ISSN 0268-005X
    Acid induced - Enzymatic hydrolysis - Fermentation - Gelation - Pea protein

    In the light of changing nutritional trends and recommendations, yoghurt style gels from plant proteins are a promising way to incorporate relevant amounts of plant derived proteins into the diet. However, in order to attain a high level of consumer acceptance, a thorough understanding of rheological behaviour, involved protein fractions and relevant interactions is mandatory in order to later be able to customise properties of fermentation induced gels. Therefore, the aim of this study was to first characterise the type of dominating interactions within the gel network and the protein fractions involved followed by determination of the rheological properties of gels made from pea protein and pea protein hydrolysates. Results showed that the protein-protein interactions were mainly hydrophobic in nature and involved mostly the legumin fraction. A smaller contribution could be ascribed to electrostatic interactions between vicilin and the basic legumin-β chain, thus incorporating some vicilin into the gel. The interaction between vicilin and the basic legumin-β chain was influenced by modification of the molecular weight distribution via enzymatic hydrolysis. Especially hydrolysis with trypsin led to an enhanced involvement of vicilin in the gel structure due to the increased availability of legumin-β. The molecular weight distribution only had a minor impact on the rheological properties of the fermentation induced pea protein gels leading to the conclusion that in rheology the type of interactions is more important, than the protein fractions involved.

    Competition of electrogens with methanogens for hydrogen in bioanodes
    Georg, S. ; Eguren Cordoba, I. de; Sleutels, T. ; Kuntke, P. ; Heijne, A. ter; Buisman, C.J.N. - \ 2020
    Water Research 170 (2020). - ISSN 0043-1354
    Bioanode - Bioelectrochemical system - Fermentation - Hydrogen oxidation

    Bioelectrochemical systems (BES) can provide an energy efficient way to recover nutrients from wastewaters. However, the electron donors available in wastewater are often not sufficient to recover the total amount of nutrients. This work investigates hydrogen (H2) as an additional substrate for bioanodes. This hydrogen can be produced in the fermentation of complex organic waste or could be recycled from the cathode. Understanding how to influence the competition of electroactive microorganisms (EAM) with methanogens for H2 gas from different sources is key to successful application of H2 as additional electron donor in bioelectrochemical nutrient recovery. Ethanol (EtOH) was used as model compound for complex wastewaters since it is fermented into both acetate and H2. EtOH was efficiently converted into electricity (e) by a syntrophic biofilm. Total recovered charge from 1 mM EtOH was 20% higher than for the same amount of acetate. This means that H2 from EtOH fermentation was converted by EAM into electricity. Low EtOH concentrations (1 mM) led to higher conversion efficiencies into electricity than higher concentrations (5 and 10 mM). Thermodynamic calculations show this correlates with a higher energy gain for electrogens compared to methanogens at low H2 concentrations. Cumulatively adding 1 mM EtOH without medium exchange (14 times in 14 days) resulted in stable conversion of H2 to e (67%–77% e) rather than methane. With H2 gas as electron donor, 68 ± 2% H2 was converted into e with no carbon source added, and still 53 ± 5% to e when 50 mM bicarbonate was provided. These results show that under the provided conditions, electrogens can outcompete methanogens for H2 as additional electron donor in MECs for nutrient recovery.

    Untargeted mass spectrometry-based metabolomics approach unveils molecular changes in raw and processed foods and beverages
    Gauglitz, Julia M. ; Aceves, Christine M. ; Aksenov, Alexander A. ; Aleti, Gajender ; Almaliti, J. ; Bouslimani, A. ; Brown, Elizabeth A. ; Campeau, Anaamika ; Caraballo-Rodríguez, Andrés Mauricio ; Chaar, Rama ; Silva, Ricardo R. da; Demko, Alyssa M. ; Ottavio, Francesca Di; Elijah, Emmanuel ; Ernst, Madeleine ; Ferguson, L.P. ; Holmes, Xavier ; Jarmusch, Alan K. ; Jiang, Lingjing ; Kang, Kyo Bin ; Koester, I. ; Kwan, B. ; Li, Jie ; Li, Yueying ; Melnik, Alexey V. ; Molina-Santiago, Carlos ; Ni, B. ; Oom, Aaron L. ; Panitchpakdi, Morgan W. ; Petras, Daniel ; Quinn, Robert ; Sikora, Nicole ; Spengler, Katharina ; Teke, B. ; Tripathi, Anupriya ; Ul-Hasan, S. ; Hooft, Justin J.J. van der; Vargas, Fernando ; Vrbanac, Alison ; Vu, Anthony Q. ; Wang, Steven C. ; Weldon, K. ; Wilson, K. ; Wozniak, Jacob M. ; Yoon, Michael ; Bandeira, Nuno ; Dorrestein, Pieter C. - \ 2020
    Food Chemistry 302 (2020). - ISSN 0308-8146
    Fermentation - Food - LC-MS/MS - Metabolomics - Molecular networking - Tea - Untargeted mass spectrometry - Yogurt

    In our daily lives, we consume foods that have been transported, stored, prepared, cooked, or otherwise processed by ourselves or others. Food storage and preparation have drastic effects on the chemical composition of foods. Untargeted mass spectrometry analysis of food samples has the potential to increase our chemical understanding of these processes by detecting a broad spectrum of chemicals. We performed a time-based analysis of the chemical changes in foods during common preparations, such as fermentation, brewing, and ripening, using untargeted mass spectrometry and molecular networking. The data analysis workflow presented implements an approach to study changes in food chemistry that can reveal global alterations in chemical profiles, identify changes in abundance, as well as identify specific chemicals and their transformation products. The data generated in this study are publicly available, enabling the replication and re-analysis of these data in isolation, and serve as a baseline dataset for future investigations.

    Effect of natural fermentation on nutritional composition and anti-nutrients in soy-wara (A Nigerian fried soy-cheese)
    Adeyeye, S.A.O. ; Bolaji, O.T. ; Abegunde, T.A. ; Tiamiyu, H.K. ; Adebayo-Oyetoro, A.O. ; Idowu-Adebayo, F. - \ 2020
    Food Research 4 (2020)1. - ISSN 2550-2166 - p. 152 - 160.
    Fermentation - Nutritional and anti-nutrients - Soy-wara - Soybeans

    This study was carried to evaluate the effect of natural fermentation on nutritional composition and anti-nutrients in soy-wara. A total of 100 samples consisting of five treatments of 20 samples per each treatment were studied. Yellow soybeans were soaked and fermented for 24 hrs, 48 hrs, 72 hrs and 96 hrs respectively at 27±2°C with 0 hr as control. Fermented soybeans were used for soy-wara production and soy-wara samples were evaluated for nutritional (amino acid, vitamin and mineral profile) and anti-nutritional (phytate, tannin and trypsin inhibitor activity) qualities. Results of amino acids analysis showed that tryptophan, isoleucine, methionine, phenylalanine, leucine and lysine contents in the fermented soy-wara ranged from 3.49 to 6.75, 21.94 to 24.41, 20.60 to 23.98, 22.11 to 27.15, 33.16 to 36.51 and 24.16 to 26.27 mg/100 g respectively. The values of thiamine, riboflavin and niacin contents in the fermented soy-wara ranged from 1.60 to 1.87, 1.44 to 1.71 and 2.21 to 2.78 mg/100 g respectively. The mineral elements calcium, iron, potassium, sodium, phosphorus and magnesium contents in the fermented soy-wara ranged from 17.65 to 19.08, 6.94 to 8.41, 29.76 to 30.69, 8.31 to 9.42, 27.52 to 28.55 and 21.02 to 24.83 mg/100 g respectively. Soaking and fermentation reduced the tannin content from 115.64 to 43.26 mg/100 g; phytate content from 153.81 to 47.16 mg/100 g, trypsin inhibitor from 96.56 to 1.10 mg/100 g and protease inhibitor from 98.11 to 1.2 mg/100 g respectively. In conclusion, natural fermentation of the legume reduced anti-nutritional factors and improved the nutrient composition of the product.

    Degradation of fibres from fruit by-products allows selective modulation of the gut bacteria in an in vitro model of the proximal colon
    Bussolo de Souza, Carlota ; Jonathan, Melliana ; Isay Saad, Susana Marta ; Schols, Henk A. ; Venema, Koen - \ 2019
    Journal of Functional Foods 57 (2019). - ISSN 1756-4646 - p. 275 - 285.
    Degradation - Fermentation - Fibre - Fruit by-products - Gut microbiota - SCFA

    The potential prebiotic effect of fibres (alcohol insoluble solids fractions) from fruit by-products – orange bagasses and passion fruit peels – and their degradation by human gut microbiota was tested in an in vitro colon system. Standard medium and inulin were used as controls. Orange bagasses (A-OB1 and A-OB2) had similar chemical composition but differed regarding fermentation profile. A-OB2 resulted in a more diverse bacterial community than A-OB1 and produced more SCFA, with increased Ruminococcus and Lachnospira. Carbohydrate utilization was higher on A-OB2 probably due to higher ratio soluble to insoluble fibres. Isolated fibres from passion fruit peels presented similar chemical composition and fermentation profiling. Bacteroides and Ruminococcus were the main genera stimulated. Negligible lactate and succinate production represent slow fermentation, a protective feature against colon cancer. This study provided evidence that the tested fruit by-products have the potential to be used for selective modulation of the gut microbiota.

    Application of a partial cell recycling chemostat for continuous production of aroma compounds at near-zero growth rates
    Mastrigt, Oscar van; Egas, Reinier A. ; Lillevang, Søren K. ; Abee, Tjakko ; Smid, Eddy J. - \ 2019
    BMC Research Notes 12 (2019)1. - ISSN 1756-0500
    Continuous cultivation - Fermentation - Lactic acid bacteria - Maintenance - Metabolomics - Retentostat - VOC

    Objective: The partial cell recycling chemostat is a modification of the chemostat in which cells are partially recycled towards the bioreactor. This allows using dilution rates higher than the maximum growth rate resulting in higher biomass concentrations and increased process rates. In this study, we demonstrate with a single observation that this system can also be used to study microorganisms at near-zero growth rates and as production system for compounds specific for slow growth, such as those typical for ripened cheese. Results: Lactococcus lactis FM03-V2 was cultivated at growth rates between 0.0025 and 0.025 h -1 . Detailed analysis of produced aroma compounds revealed that levels of particular compounds were clearly affected by the growth rate within the studied range demonstrating that we can steer the aroma production by controlling the growth rate. With this approach, we also experimentally validated that the maintenance coefficient of this dairy strain decreased at near-zero growth rates (6.4-fold). An exponentially decreasing maintenance coefficient was included in the growth model, enabling accurate prediction of biomass accumulation in the partial cell recycling chemostat. This study demonstrates the potential of partial cell recycling chemostat both as aroma production system at near-zero growth rates and as unique research tool.

    Robust sampling and preservation of DNA for microbial community profiling in field experiments
    Groenenboom, Anneloes E. ; Smid, Eddy J. ; Schoustra, Sijmen E. - \ 2019
    BMC Research Notes 12 (2019)1. - ISSN 1756-0500
    DNA stabilisation - Fermentation - Field trial - Filter paper disks - Microbial community - Milk

    Objective: Stabilising samples of microbial communities for DNA extraction without access to laboratory equipment can be a challenging task. In this paper we propose a method using filter paper disks for the preservation of DNA from diverse microbial communities which are found in a fermented milk product. Results: Small adaptations to the DNA extraction method used for liquid fermented milk delivered DNA of sufficient amounts and quality to be used for later analyses, e.g. full community 16S amplicon sequencing. The microbial community structure obtained via the filter paper method showed sufficient resemblance to the structure obtain via the traditional DNA extraction from the liquid milk sample. This method can therefore successfully be used to analyse diverse microbial communities from fermented milk products from remote areas.

    Aroma formation in retentostat co-cultures of Lactococcus lactis and Leuconostoc mesenteroides
    Mastrigt, Oscar van; Egas, Reinier A. ; Abee, Tjakko ; Smid, Eddy J. - \ 2019
    Food Microbiology 82 (2019). - ISSN 0740-0020 - p. 151 - 159.
    Cheese - Fermentation - Interaction - Mixed culture - Near-zero growth rate

    Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides are considered to be the main aroma producers in Dutch-type cheeses. Both species of lactic acid bacteria were grown in retentostat mono- and co-cultures to investigate their interaction at near-zero growth rates and to determine if co-cultivation enhances the aroma complexity compared to single species performance. During retentostat mono-cultures, the growth rates of both species decreased to less than 0.001 h −1 and a large fraction of the cells became viable but not culturable. Compared to Lc. mesenteroides, L. lactis reached a 3.4-fold higher biomass concentration caused by i) a higher ATP yield on substrate, ii) a higher biomass yield on ATP and iii) a lower maintenance requirement (m ATP ). Dynamic models estimated that the m ATP of both species decreased approximately 7-fold at near-zero growth rates compared to high growth rates. Extension of these models by assuming equal substrate distribution resulted in excellent prediction of the biomass accumulation in retentostat co-cultures with L. lactis dominating (100:1) as observed in ripened cheese. Despite its low abundance (∼1%), Lc. mesenteroides contributed to aroma production in co-cultures as indicated by the presence of all 5 specific Lc. mesenteroides compounds. This study provides insights in the production of cheese aroma compounds outside the cheese matrix by co-cultures of L. lactis and Lc. mesenteroides, which could be used as food supplements in dairy or non-dairy products.

    Effect of fermentation on content, molecule weight distribution and viscosity of β-glucans in oat sourdough
    Lu, Jun ; Shan, Lingke ; Xie, Yiting ; Min, Fangfang ; Gao, Jinyan ; Guo, Laichun ; Ren, Changzhong ; Yuan, Juanli ; Gilissen, Luud ; Chen, Hongbing - \ 2019
    International Journal of Food Science and Technology 54 (2019)1. - ISSN 0950-5423 - p. 62 - 67.
    Fermentation - Lactobacillus plantarum - Oat β-glucan - Sourdough - Viscosity

    This study investigated the effect of fermentation on the physicochemical properties of β-glucans in oat sourdough. Sourdoughs were produced from oat using homo-fermentative lactic acid bacteria, Lactobacillus plantarum 22134. The contents of total β-glucan and soluble β-glucan, the molecular weight (MW) of β-glucan and the viscosity of the extracted β-glucans were determined at 0, 4, 8, 10 and 12 h of fermentation. The total β-glucan content decreased from 4.89% to 4.23% after 12 h of fermentation. The soluble β-glucan concentration increased from 1.89% to 2.18% and then decreased to 1.97% after 8 h of fermentation. The content of β-glucans with MW > 105 decreased from 0 to 4 h of fermentation, followed by an increase and then a decrease after 8 h. The oat sourdough fermented for 8 h had high viscosity, which could be more beneficial for health and bread texture quality, especially for gluten-free breads. International Journal of Food Science and Technology

    Aroma formation during cheese ripening is best resembled by Lactococcus lactis retentostat cultures
    Mastrigt, Oscar van; Gallegos Tejeda, Diego ; Kristensen, Mette N. ; Abee, Tjakko ; Smid, Eddy J. - \ 2018
    Microbial Cell Factories 17 (2018)1. - ISSN 1475-2859
    Fermentation - Metabolism - VOC - Zero growth

    Background: Cheese ripening is a complex, time consuming and expensive process, which involves the generation of precursors from carbohydrates, proteins and fats and their subsequent conversion into a wide range of compounds responsible for the flavour and texture of the cheese. This study aims to investigate production of cheese aroma compounds outside the cheese matrix that could be applied for instance as food supplements in dairy or non-dairy products. Results: In this study, aroma formation by a dairy Lactococcus lactis was analysed as a function of the growth medium [milk, hydrolysed micellar casein isolate (MCI) and chemically defined medium (CDM)] and the cultivation conditions (batch culture, retentostat culture and a milli-cheese model system). In the retentostat cultures, the nutrient supply was severely restricted resulting in low growth rates (~ 0.001 h-1), thereby mimicking cheese ripening conditions in which nutrients are scarce and bacteria hardly grow. In total 82 volatile organic compounds were produced by the bacteria. Despite the use of a chemically defined medium, retentostat cultures had the biggest qualitative overlap in aroma production with the milli-cheese model system (36 out of 54 compounds). In the retentostat cultures, 52 known cheese compounds were produced and several important cheese aroma compounds and/or compounds with a buttery or cheese-like aroma increased in retentostat cultures compared to batch cultures and milli-cheeses, such as esters, methyl ketones, diketones and unsaturated ketones. In cultures on CDM and MCI, free fatty acids and their corresponding degradation products were underrepresented compared to what was found in the milli-cheeses. Addition of a mixture of free fatty acids to CDM and MCI could help to enhance flavour formation in these media, thereby even better resembling flavour formation in cheese. Conclusions: This study demonstrates that retentostat cultivation is the preferred method to produce cheese flavours outside the cheese matrix by mimicking the slow growth of bacteria during cheese ripening.

    Microencapsulated Starter Culture During Yoghurt Manufacturing, Effect on Technological Features
    Prisco, Annachiara de; Valenberg, Hein J.F. van; Fogliano, Vincenzo ; Mauriello, Gianluigi - \ 2017
    Food Bioprocess Technology 10 (2017)10. - ISSN 1935-5130 - p. 1767 - 1777.
    Cell physiology - Fermentation - Microencapsulation - Probiotic - Volatile metabolites

    The potential of living cell microencapsulation in sustaining cells’ viability, functionality and targeted release in gastrointestinal tract is relatively well documented. Differently, the effects exerted by the capsules on cell metabolic activities during fermentation of a food matrix as well as on cell physiology are poorly addressed. This paper aimed at studying the effects of chitosan-alginate capsules (matrix and core-shell) on metabolic activities of Streptococcus thermophilus and probiotic Lactobacillus delbrueckii during milk fermentation for yoghurt production. This food system has been used to monitor growth, acidification kinetics and strain proteolytic activity. Bacterial viability has been monitored during yoghurt storage at 4 °C for 28 days and an in vitro digestion to evaluate the protective effect exerted by the capsules. Furthermore, production of volatile metabolites associated with starter culture activity was monitored by headspace solid-phase microextraction-GC/MS to explore possible influence of microenvironment on cell metabolism. Results indicate that both kinds of capsules influenced at different extent cell functionalities (growth, acidification and proteolysis), while they improve cell viability during yoghurt storage and simulated gastrointestinal passage. The volatile pattern revealed that capsules influenced their production in yoghurt: 12 out of 28 volatiles recovered in yoghurt fermented by free and encapsulated starters had significantly different concentration. However, concentration of the main aroma constituents (e.g. acetaldehyde, diacetyl, acetoin) was not significantly affected. Due to the leakage of bacteria from microcapsules during fermentation, the final product resulted in co-existing of free and still encapsulated cells, with the main advantage of an increased viability during yoghurt storage and simulated digestion of the encapsulated counterpart.

    Streptococcus caviae sp. nov., isolated from Guinea pig faecal samples
    Palakawong Na Ayudthaya, Susakul ; Hilderink, Loes J. ; Oost, John van der; Vos, Willem M. de; Plugge, Caroline M. - \ 2017
    International Journal of Systematic and Evolutionary Microbiology 67 (2017)5. - ISSN 1466-5026 - p. 1551 - 1556.
    Cellobiose - Dried grass - Fermentation - Inulin - Lactic acid - Streptococcus

    A novel cellobiose-degrading and lactate-producing bacterium, strain Cavy grass 6T, was isolated from faecal samples of guinea pigs (Cavia porcellus). Cells of the strain were ovalshaped, non-motile, non-spore-forming, Gram-stain-positive and facultatively anaerobic. The strain gr at 25–40 °C (optimum 37 °C) and pH 4.5–9.5 (optimum 8.0). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Cavy grass 6T belongs to the genus Streptococcus with its closest relative being Streptococcus devriesei CCUG 47155T with only 96.5% similarity. Comparing strain Cavy grass 6T and Streptococcus devriesei CCUG 47155T, average nucleotide identity and level of digital DNA–DNA hybridization dDDH were only 86.9 and 33.3%, respectively. Housekeeping genes groEL and gyrA were different between strain Cavy grass 6T and other streptococci. The G+C content of strain Cavy grass 6T was 42.6±0.3 mol%. The major (>10%) cellular fatty acids of strain Cavy grass 6T were C16:0, C20: 1ω9c and summed feature 8 (C18: 1ω7c and/or C18: 1ω6c). Strain Cavy grass 6T ferment a range of plant mono- and disaccharides as well as polymeric carbohydrates, including cellobiose, dulcitol, D-glucose, maltose, raffinose, sucrose, L-sorbose, trehalose, inulin and dried grass extract, to lactate, formate, acetate and ethanol. Based on phylogenetic and physiological characteristics, Cavy grass 6T can be distinguished from other members of the genus Streptococcus. Therefore, a novel species of the genus Streptococcus, family Streptococcaceae, order Lactobacillales is proposed, Streptococcus caviae sp. nov. (type strain Cavy grass 6T=TISTR 2371T=DSM 102819T).

    A novel millet-based probiotic fermented food for the developing world
    Stefano, Elisa Di; White, Jessica ; Seney, Shannon ; Hekmat, Sharareh ; McDowell, Tim ; Sumarah, Mark ; Reid, Gregor - \ 2017
    Nutrients 9 (2017)5. - ISSN 2072-6643
    Cereal - Fermentation - Millet - Probiotic - Sub-Saharan Africa - Yogurt

    Probiotic yogurt, comprised of a Fiti sachet containing Lactobacillus rhamnosus GR-1 and Streptococcus thermophilus C106, has been used in the developing world, notably Africa, to alleviate malnutrition and disease. In sub-Saharan African countries, fermentation of cereals such as millet, is culturally significant. The aim of this study was to investigate the fermentation capability of millet when one gram of the Fiti sachet consortium was added. An increase of 1.8 and 1.4 log CFU/mL was observed for S. thermophilus C106 and L. rhamnosus GR-1 when grown in 8% millet in water. Single cultures of L. rhamnosus GR-1 showed the highest _max when grown in the presence of dextrose, galactose and fructose. Single cultures of S. thermophilus C106 showed the highest _max when grown in the presence of sucrose and lactose. All tested recipes reached viable counts of the probiotic bacteria, with counts greater than 106 colony-forming units (CFU)/mL. Notably, a number of organic acids were quantified, in particular phytic acid, which was shown to decrease when fermentation time increased, thereby improving the bioavailability of specific micronutrients. Millet fermented in milk proved to be the most favorable, according to a sensory evaluation. In conclusion, this study has shown that sachets being provided to African communities to produce fermented milk, can also be used to produce fermented millet. This provides an option for when milk supplies are short, or if communities wish to utilize the nutrient-rich qualities of locally-grown millet.

    In-situ carboxylate recovery and simultaneous pH control with tailor-configured bipolar membrane electrodialysis during continuous mixed culture fermentation
    Arslan, D. ; Zhang, Y. ; Steinbusch, K.J.J. ; Diels, L. ; Hamelers, Hubertus V.M. ; Buisman, C.J.N. ; Wever, H. de - \ 2017
    Separation and Purification Technology 175 (2017). - ISSN 1383-5866 - p. 27 - 35.
    Bipolar membrane - Electrodialysis - Fermentation - ISPR - Short chain carboxylates

    Anaerobic fermentation of organic waste streams by mixed culture generates a mixture of short chain carboxylic acids. To avoid inhibitory effects of the acids or their consumption in internal conversion reactions in the mixed culture environment, in-situ recovery of acids can be beneficial. In this study, electrodialysis with bipolar membranes (EDBM) was applied to a mixed culture fermentation on organic waste streams using a novel EDBM stack with “direct contact” operation mode. We could demonstrate simultaneous recovery of carboxylates from the fermenter by the EDBM stack while in-situ generation and transport of hydroxyl ions to the fermenter allowed direct pH control. Experiments showed productivity increase after EDBM coupling to the fermenter, and complete elimination of external base consumption. It was also observed that EDBM was able to drive the mixed culture fermentation towards acetate and propionate type of carboxylates.

    Effects of pectin on fermentation characteristics, carbohydrate utilization, and microbial community composition in the gastrointestinal tract of weaning pigs
    Tian, Lingmin ; Bruggeman, Geert ; Berg, Marco van den; Borewicz, Klaudyna ; Scheurink, Anton J.W. ; Bruininx, Erik ; Vos, Paul de; Smidt, Hauke ; Schols, Henk A. ; Gruppen, Harry - \ 2017
    Molecular Nutrition & Food Research 61 (2017)1. - ISSN 1613-4125
    Autoclave soybean meal - Dietary fiber - Digestibility - Fermentation - Microbiota composition

    Scope: We aimed to investigate the effects of three different soluble pectins on the digestion of other consumed carbohydrates, and the consequent alterations of microbiota composition and SCFA levels in the intestine of pigs. Methods and results: Piglets were fed a low-methyl esterified pectin enriched diet (LMP), a high-methyl esterified pectin enriched diet (HMP), a hydrothermal treated soybean meal enriched diet (aSBM) or a control diet (CONT). LMP significantly decreased the ileal digestibility of starch resulting in more starch fermentation in the proximal colon. In the ileum, low-methyl esterified pectin present was more efficiently fermented by the microbiota than high-methyl esterified pectin present which was mainly fermented by the microbiota in the proximal colon. Treated soybean meal was mainly fermented in the proximal colon and shifted the fermentation of cereal dietary fiber to more distal parts, resulting in high SCFA levels in the mid colon. LMP, HMP, and aSBM decreased the relative abundance of the genus Lactobacillus and increased that of Prevotella in the colon. Conclusion: The LMP, HMP, and aSBM, differently affected the digestion processes compared to the control diet and shaped the colonic microbiota from a Lactobacillus-dominating flora to a Prevotella-dominating community, with potential health-promoting effects.

    Production of L(+)-lactic acid from acid pretreated sugarcane bagasse using Bacillus coagulans DSM2314 in a simultaneous saccharification and fermentation strategy
    Pol, Edwin C. van der; Eggink, Gerrit ; Weusthuis, Ruud A. - \ 2016
    Biotechnology for Biofuels 9 (2016). - ISSN 1754-6834 - 12 p.
    Bagasse - Enzymatic hydrolysis - Fermentation - Lactic acid - Lignocellulose - Simultaneous saccharification and fermentation (SSF)

    Background: Sugars derived from lignocellulose-rich sugarcane bagasse can be used as feedstock for production of L(+)-lactic acid, a precursor for renewable bioplastics. In our research, acid-pretreated bagasse was hydrolysed with the enzyme cocktail GC220 and fermented by the moderate thermophilic bacterium Bacillus coagulans DSM2314. Saccharification and fermentation were performed simultaneously (SSF), adding acid-pretreated bagasse either in one batch or in two stages. SSF was performed at low enzyme dosages of 10.5-15.8 FPU/g DW bagasse. Results: The first batch SSF resulted in an average productivity of 0.78 g/l/h, which is not sufficient to compete with lactic acid production processes using high-grade sugars. Addition of 1 g/l furfural to precultures can increase B. coagulans resistance towards by-products present in pretreated lignocellulose. Using furfural-containing precultures, productivity increased to 0.92 g/l/h, with a total lactic acid production of 91.7 g in a 1-l reactor containing 20% W/W DW bagasse. To increase sugar concentrations, bagasse was solubilized with a liquid fraction, obtained directly after acid pretreatment. Solubilizing the bagasse fibres with water increased the average productivity to 1.14 g/l/h, with a total lactic acid production of 84.2 g in a 1-l reactor. Addition of bagasse in two stages reduced viscosity during SSF, resulting in an average productivity in the first 23 h of 2.54 g/l/h, similar to productivities obtained in fermentations using high-grade sugars. Due to fast accumulation of lactic acid, enzyme activity was repressed during two-stage SSF, resulting in a decrease in productivity and a slightly lower total lactic acid production of 75.6 g. Conclusions: In this study, it is shown that an adequate production of lactic acid from lignocellulose was successfully accomplished by a two-stage SSF process, which combines acid-pretreated bagasse, B. coagulans precultivated in the presence of furfural as microorganism, and GC220 as enzyme cocktail. The process may be further improved by enhancing enzyme hydrolysis activities at high lactic acid concentrations.

    Isolation of a genetically accessible thermophilic xylan degrading bacterium from compost
    Daas, Tijn ; Weijer, Tom van de; Vos, Willem M. de; Oost, John van der; Kranenburg, Richard van - \ 2016
    Biotechnology for Biofuels 9 (2016). - ISSN 1754-6834
    CMC - Compost - Electroporation - Fermentation - Geobacillus - Lactic acid - Thermophile - Xylan

    Background: Due to the finite nature of global oil resources we are now faced with the challenge of finding renewable resources to produce fuels and chemicals in the future. Lactic acid has great potential as a precursor for the production of bioplastics alternatives to conventional plastics. Efficient lactic acid fermentation from non-food lignocellulosic substrates requires pretreatment and saccharification to generate fermentable sugars. A fermentation process that requires little to no enzyme additions, i.e. consolidated bioprocessing would be preferred and requires lactic acid-producing organisms that have cellulolytic and/or hemicellulolytic activity. Results: To obtain candidate production strains we have enriched and isolated facultative anaerobic (hemi) cellulolytic bacterial strains from compost samples. By selecting for growth on both cellulose and xylan, 94 Geobacillus strains were isolated. Subsequent screening for lactic acid production was carried out from C6 and C5 sugar fermentations and a selection of the best lactic acid producers was made. The denitrifying Geobacillus thermodenitrificans T12 was selected for further research and was rendered genetically accessible. In fermentations on a mixture of glucose and xylose, a total of 20.3 g of lactic acid was produced with a yield of 0.94 g product/g sugar consumed. In addition, strain T12 is capable of direct conversion of beech wood xylan to mainly lactic acid in minimal media. Conclusions: We have demonstrated that G. thermodenitrificans T12 is genetically accessible and produces lactic acid as its main fermentation product on glucose, xylose and a mixture thereof. Strain T12 was additionally used for the direct conversion of xylan to lactic acid. The genetic accessibility of the T12 strain provides a solid basis for the development of this strain into a host for consolidated bioprocessing of biomass to lactic acid.

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