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Industrial Production and Applications of Yeast and Yeast Products
Published in Devarajan Thangadurai, Jeyabalan Sangeetha, Industrial Biotechnology, 2017
Rebecca S. Thombre, Sonali Joshi
Yeast produce larger cell size as compared to bacteria and demonstrate typical spherical, oval, elliptical or elongate cells ranging from 5–10 µm in size. Nutritionally yeasts are typical chemoheterotrophic organisms. They obtain energy by oxidation of organic compounds. They utilize carbohydrate sugars like hexoses and pentoses (Barnett, 1975). Yeasts are aerobic organisms and some species are facultative anaerobes. The yeast cell wall is composed of phosphorylated mannan, mannan, β-glucan, chitin and mannoprotein. The pH optimum for cultivation of yeast is around 5–7.5; however some species may be able to survive at a broader pH range. Similarly, most yeast grows optimally at room temperature, however yeast can tolerate high temperatures (Bakers yeast) and also low temperature (Watson, 1976). The common medium used for cultivation of yeast are Saborauds medium, Potato dextrose agar, Glucose yeast extract agar and Malt agar. The role of yeast in fermentation was described by Louis Pasteur. Since then, yeasts have been well known for the role as starter cultures in fermentations. Yeast can metabolize hexose sugar (glucose) via the glycolytic sequence (Embden Mayerhoff pathway). Some yeast like Zymomonas sp. utilizes the Entner-Duodorhoff pathway for breakdown of glucose to pyruvate. The key enzyme that yeast utilize in alcoholic fermentation is alcohol dehydrogenase.
Biochar effects on the abundance, activity and diversity of the soil biota
Published in Johannes Lehmann, Stephen Joseph, Biochar for Environmental Management, 2015
Janice E. Thies, Matthias C. Rillig, Ellen R. Graber
Chemoheterotrophic soil organisms require C substrates and nutrients to support their growth and metabolism. Carbon substrates supply both energy and cell C for biosynthesis. Biochar can alter both the quality and quantity of C substrates available in soil and, through its adsorptive properties, affect the availability of key nutrient elements. The effects of biochar amendments on soil microbial activity have been assessed across a range of biochar and soil types and include effects on CO2 evolution, largely resulting from microbial respiration (Table 13.1), activity of soil enzymes (Table 13.2) and N transformations (N mineralization, nitrification, denitrification and nitrogen fixation) (Table 13.3). Changes in these processes observed in biochar-amended soils and the potential mechanisms involved are discussed below.
Causes and Effects of Performance Deterioration: The Lineup
Published in Stuart A. Smith, MONITORING and REMEDIATION WELLS, 2017
A variety of environmental gradients can be expected to be formed by biogeochemical processes in aquifers. Such processes are enhanced in aquifers with organic concentrations. These may be sufficient to encourage microbial growth and sharp changes in redox potential. These gradients facilitate (or are the product of) a variety of microbial activities. This variety is reflected in a high overall microbial diversity in relatively “rich” groundwater, although single species may dominate locally. Fermentation, chemoheterotrophic oxidation of organics, and both oxidation and reduction of minerals and metals are practiced by microorganisms all living in close proximity.
Modification of media using food-grade components for the fermentation of Bifidobacterium and Lactobacillus strains in large-scale bioreactors
Published in Preparative Biochemistry & Biotechnology, 2020
Chayanee Boontun, Savitri Vatanyoopaisarn, Sungwarn Hankla, Eisuke Kuraya, Yasutomo Tamaki
Before using the media with modified components, both probiotic strains were first cultured in small-scale, 30-ml batch fermentation using commercial MRS medium plus 0.05% (w/v) L-cysteine HCl. The specific growth rates of B. animalis subsp. lactis KMP-H9-01 and L. reuteri KMP-P4-S03 were 0.29 and 0.58 (h−1). More data has been provided in Supplementary Table S2. Three food-grade carbon sources were compared for their influence on the cell propagation of both probiotics. The results are displayed in Figure 1. The highest cell numbers appeared after 24 h of incubation for both strains and for all C sources. However, the B. animalis subsp. lactis KMP-H9-01 equally utilized either glucose or sucrose for growth. The maximum cell numbers were within 9.1–9.2 log10 CFU/ml (Figure 1A). Besides, the cell viability was the same for up to 48 h, except for the medium with 5 g/l glucose. In contrast to L. reuteri KMP-P4-S03, the cell numbers increased according to the amount of the carbon source supplied (Figure 1B) (particularly for glucose and XOS). The maximum cell numbers were 8.7 and 8.8 log10 CFU/ml when using 15 and 20 g/l of sucrose, respectively. The viable cells of L. reuteri KMP-P4-S03 noticeably decreased more in glucose than sucrose at 48 h. For XOS, the highest cell numbers were 9.2 and 8.2 log10 CFU/ml for B. animalis subsp. lactis KMP-H9-01 and L. reuteri KMP-P4-S03, respectively, when amounts ≥15 g/l were used. In addition, the carbon source is used as an energy source for chemoheterotrophic bacteria, and the rate of carbon metabolism can influence the formation of biomass.[17] XOS is a prebiotic that consists of less than 10 molecules of xylose linked by ß-(1-4) bonds.[34] Based on Table 2, both strains slowly used D-xylose, and L-xylose was not fermented. The bacteria may contain enzymes to break ß-(1-4) bonds; however, the incapability to employ xylose effectively could hinder the growth rate. Although a report supported the use of XOS as a prebiotic for bifidobacteria, not all species can effectively utilize it.[35] Other research has shown that XOS is more favorable for the growth of bifidobacteria in the colon microbiota than lactobacilli.[36] This agreed with the results of this study showing that B. animalis subsp. lactis KMP-H9-01 grew better at 24 h than L. reuteri KMP-P4-S03. Moreover, when considering the price per kg of the three carbohydrates used in this experiment, sucrose was the least expensive. Therefore, sucrose (15 g/l) was selected as a carbon source for both strains in the following experiment.