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Fermentation, Volume 2, Issue 3 (September 2016) – 4 articles

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919 KiB  
Article
Use of Nutritional Requirements for Brettanomyces bruxellensis to Limit Infections in Wine
by Nicolas H. Von Cosmos and Charles G. Edwards
Fermentation 2016, 2(3), 17; https://doi.org/10.3390/fermentation2030017 - 9 Sep 2016
Cited by 10 | Viewed by 7194
Abstract
Specific vitamin requirements of the wine spoilage yeast, Brettanomyces bruxellensis, were evaluated. Previous studies had not taken into influences of ethanol or nutrient carry-over between sequential transfers into vitamin-omitted media. Knowing nutritional needs, limiting growth of the yeast in wine by selective [...] Read more.
Specific vitamin requirements of the wine spoilage yeast, Brettanomyces bruxellensis, were evaluated. Previous studies had not taken into influences of ethanol or nutrient carry-over between sequential transfers into vitamin-omitted media. Knowing nutritional needs, limiting growth of the yeast in wine by selective removal of important vitamins was investigated. Six strains of B. bruxellensis were grown and sequentially transferred into single vitamin-omitted media. None of the strains required p-aminobenzoic acid, folic acid, nicotinic acid, myo-inositol, pantothenic acid, or riboflavin. While some needed thiamin depending on the absence/presence of ethanol, growth of all strains was greatly affected by biotin. Here, concentrations ≥0.2 µg/L were required to achieve yeast populations >106 cfu/mL for high (104 cfu/mL) or low (102 cfu/mL) initial inoculums. At concentrations <0.2 µg/L, culturabilities either remained unchanged or increased less than two logs after 40 days. Since the protein avidin binds irreversibly to biotin, egg whites containing avidin or the purified protein were added to a wine to diminish bioavailability of the vitamin. While biotin concentrations were reduced, populations of B. bruxellensis achieved were decreased by one to three logs, thereby supporting further development of biotin depletion strategies in winemaking. Full article
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575 KiB  
Article
Batch Fermentation Options for High Titer Bioethanol Production from a SPORL Pretreated Douglas-Fir Forest Residue without Detoxification
by Mingyan Yang, Hairui Ji and J.Y. Zhu
Fermentation 2016, 2(3), 16; https://doi.org/10.3390/fermentation2030016 - 11 Aug 2016
Cited by 6 | Viewed by 5999
Abstract
This study evaluated batch fermentation modes, namely, separate hydrolysis and fermentation (SHF), quasi-simultaneous saccharification and fermentation (Q-SSF), and simultaneous saccharification and fermentation (SSF), and fermentation conditions, i.e., enzyme and yeast loadings, nutrient supplementation and sterilization, on high titer bioethanol production from SPORL-pretreated Douglas-fir [...] Read more.
This study evaluated batch fermentation modes, namely, separate hydrolysis and fermentation (SHF), quasi-simultaneous saccharification and fermentation (Q-SSF), and simultaneous saccharification and fermentation (SSF), and fermentation conditions, i.e., enzyme and yeast loadings, nutrient supplementation and sterilization, on high titer bioethanol production from SPORL-pretreated Douglas-fir forest residue without detoxification. The results indicated that Q-SSF and SSF were obviously superior to SHF operation in terms of ethanol yield. Enzyme loading had a strong positive correlation with ethanol yield in the range studied. Nutrient supplementation and sterility were not necessary for ethanol production from SPORL-pretreated Douglas-fir. Yeast loading had no substantial influence on ethanol yield for typical SSF conditions. After 96 h fermentation at 38 °C on shake flask at 150 rpm, terminal ethanol titer of 43.2 g/L, or 75.1% theoretical based on untreated feedstock glucan, mannan, and xylan content was achieved, when SSF was conducted at whole slurry solids loading of 15% with enzyme and yeast loading of 20 FPU/g glucan and 1.8 g/kg (wet), respectively, without nutrition supplementation and sterilization. It is believed that with mechanical mixing, enzyme loading can be reduced without reducing ethanol yield with extended fermentation duration. Full article
(This article belongs to the Special Issue Yeast Biotechnology 1.0)
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2682 KiB  
Article
Modelling and Optimization of Operational Setpoint Parameters for Maximum Fermentative Biohydrogen Production Using Box-Behnken Design
by Patrick T. Sekoai
Fermentation 2016, 2(3), 15; https://doi.org/10.3390/fermentation2030015 - 20 Jul 2016
Cited by 19 | Viewed by 5632
Abstract
Fermentative biohydrogen production has been flagged as a future alternative energy source due to its various socio-economical benefits. Currently, its production is hindered by the low yield. In this work, modelling and optimization of fermentative biohydrogen producing operational setpoint conditions was carried out. [...] Read more.
Fermentative biohydrogen production has been flagged as a future alternative energy source due to its various socio-economical benefits. Currently, its production is hindered by the low yield. In this work, modelling and optimization of fermentative biohydrogen producing operational setpoint conditions was carried out. A box-behnken design was used to generate twenty-nine batch experiments. The experimental data were used to produce a quadratic polynomial model which was subjected to analysis of variance (ANOVA) to evaluate its statistical significance. The quadratic polynomial model had a coefficient of determination (R2) of 0.7895. The optimum setpoint obtained were potato-waste concentration 39.56 g/L, pH 5.56, temperature 37.87 °C, and fermentation time 82.58 h, predicting a biohydrogen production response of 537.5 mL H2/g TVS. A validation experiment gave 603.5 mL H2/g TVS resulting to a 12% increase. The R2 was above 0.7 implying the model was adequate to navigate the optimization space. Therefore, these findings demonstrated the feasibility of conducting optimized biohydrogen fermentation processes using response surface methodology. Full article
(This article belongs to the Special Issue Biofuels and Biochemicals Production)
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519 KiB  
Review
Application of Non-Saccharomyces Yeasts to Wine-Making Process
by José Juan Mateo and Sergi Maicas
Fermentation 2016, 2(3), 14; https://doi.org/10.3390/fermentation2030014 - 23 Jun 2016
Cited by 61 | Viewed by 11143
Abstract
Winemaking is a complex process involving the interaction of different microbes. The two main groups of microorganisms involved are yeasts and bacteria. Non-Saccharomyces yeasts are present on the grape surface and also on the cellar. Although these yeasts can produce spoilage, these [...] Read more.
Winemaking is a complex process involving the interaction of different microbes. The two main groups of microorganisms involved are yeasts and bacteria. Non-Saccharomyces yeasts are present on the grape surface and also on the cellar. Although these yeasts can produce spoilage, these microorganisms could also possess many interesting technological properties which could be exploited in food processing. It has been shown that some of the metabolites that these yeasts produce may be beneficial and contribute to the complexity of the wine and secrete enzymes providing interesting wine organoleptic characteristics. On the other hand, non-Saccharomyces yeasts are the key to obtain wines with reduced ethanol content. Among secreted enzymes, β-glucosidase activity is involved in the release of terpenes to wine, thus contributing to varietal aroma while β-xylosidase enzyme is also interesting in industry due to its involvement in the degradation of hemicellulose by hydrolyzing its main heteroglycan (xylan). Full article
(This article belongs to the Special Issue Yeast Biotechnology 1.0)
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