scholarly journals KINETIC EVALUATION OF ETHANOL-TOLERANT THERMOPHILE Geobacillus thermoglucosidasius M10EXG FOR ETHANOL PRODUCTION

2016 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Eny Ida Riyanti ◽  
Peter L. Rogers
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Yeast Extract ◽  
Biomass Yield ◽  
Specific Growth ◽  
Kinetic Evaluation ◽  
Geobacillus Thermoglucosidasius ◽  
Low Level ◽  
Wide Range

Thermophiles are challenging to be studied for ethanol production using agricultural waste containing lignocellulosic materials rich in hexose and pentose. These bacteria have many advantages such as utilizing a wide range of substrates, including pentose (C5) and hexose (C6). In ethanol production, it is important to use ethanol tolerant strain capable in converting lignocellulosic hydrolysate. This study was aimed to investigate the growth profile of ethanol-tolerant thermophile Geobacillus thermoglucosidasius M10EXG using a defined growth medium consisted of single carbon glucose (TGTV), xylose (TXTV), and a mixture of glucose and xylose (TGXTV), together with the effect of yeast extract addition<br />to the media. The experiments were conducted at the School of Biotechnology and Biomolecular Sciences of The University of New South Wales, Australia on a shake flask fermentation at 60°C in duplicate experiment. Cultures were sampled every two hours and analised for their kinetic parameters including the maximum specific growth rate (µmax), biomass yield (Yx/s), ethanol and by-product yields (acetate and L-lactate) (Yp/s), and the doubling time (Td). Results showed that this strain was capable of growing on minimal medium containing glucose or xylose as a single carbon source. This strain utilized glucose and xylose simultaneously (co-fermentation), although there was glucose repression of xylose at relatively low glucose concentration (0.5% w/v), particularly when yeast extract (0.2% w/v) was added to the medium. The highest biomass yield was obtained at 0.5 g l-1 on glucose medium; the yield increased when yeast extract was added (at 0.59 g l-1). The highest specific growth rate of 0.25 was obtained in the phase I growth when the strain was grown on a mixture of glucose and xylose (0.5% : 0.5% w/v) medium. Diauxic growth was shown on the mixture of glucose, xylose, and yeast extract. The strain produced low level of ethanol (0.1 g l-1), as well as low level (0.2 g l-1) of by-products (L-lactate and acetate) after 15 hours. The results suggests its potential application for fermenting lignocellulosic agricultural wastes for ethanol production.

scholarly journals KINETIC EVALUATION OF ETHANOL-TOLERANT THERMOPHILE Geobacillus thermoglucosidasius M10EXG FOR ETHANOL PRODUCTION

2016 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Eny Ida Riyanti ◽  
Peter L. Rogers
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Yeast Extract ◽  
Biomass Yield ◽  
Specific Growth ◽  
Kinetic Evaluation ◽  
Geobacillus Thermoglucosidasius ◽  
Low Level ◽  
Wide Range

Thermophiles are challenging to be studied for ethanol production using agricultural waste containing lignocellulosic materials rich in hexose and pentose. These bacteria have many advantages such as utilizing a wide range of substrates, including pentose (C5) and hexose (C6). In ethanol production, it is important to use ethanol tolerant strain capable in converting lignocellulosic hydrolysate. This study was aimed to investigate the growth profile of ethanol-tolerant thermophile Geobacillus thermoglucosidasius M10EXG using a defined growth medium consisted of single carbon glucose (TGTV), xylose (TXTV), and a mixture of glucose and xylose (TGXTV), together with the effect of yeast extract addition<br />to the media. The experiments were conducted at the School of Biotechnology and Biomolecular Sciences of The University of New South Wales, Australia on a shake flask fermentation at 60°C in duplicate experiment. Cultures were sampled every two hours and analised for their kinetic parameters including the maximum specific growth rate (µmax), biomass yield (Yx/s), ethanol and by-product yields (acetate and L-lactate) (Yp/s), and the doubling time (Td). Results showed that this strain was capable of growing on minimal medium containing glucose or xylose as a single carbon source. This strain utilized glucose and xylose simultaneously (co-fermentation), although there was glucose repression of xylose at relatively low glucose concentration (0.5% w/v), particularly when yeast extract (0.2% w/v) was added to the medium. The highest biomass yield was obtained at 0.5 g l-1 on glucose medium; the yield increased when yeast extract was added (at 0.59 g l-1). The highest specific growth rate of 0.25 was obtained in the phase I growth when the strain was grown on a mixture of glucose and xylose (0.5% : 0.5% w/v) medium. Diauxic growth was shown on the mixture of glucose, xylose, and yeast extract. The strain produced low level of ethanol (0.1 g l-1), as well as low level (0.2 g l-1) of by-products (L-lactate and acetate) after 15 hours. The results suggests its potential application for fermenting lignocellulosic agricultural wastes for ethanol production.

scholarly journals Effect of Specific Growth Rate on Fermentative Capacity of Baker’s Yeast

1998 ◽  
Vol 64 (11) ◽  
pp. 4226-4233 ◽  
Author(s):  
Pim Van Hoek ◽  
Johannes P. Van Dijken ◽  
Jack T. Pronk
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Growth Rates ◽  
Specific Growth ◽  
Pyruvate Decarboxylase ◽  
Baker's Yeast ◽  
Fermentative Capacity ◽  
Yeast Biomass ◽  
Specific Growth Rates

ABSTRACT The specific growth rate is a key control parameter in the industrial production of baker’s yeast. Nevertheless, quantitative data describing its effect on fermentative capacity are not available from the literature. In this study, the effect of the specific growth rate on the physiology and fermentative capacity of an industrialSaccharomyces cerevisiae strain in aerobic, glucose-limited chemostat cultures was investigated. At specific growth rates (dilution rates, D) below 0.28 h−1, glucose metabolism was fully respiratory. Above this dilution rate, respirofermentative metabolism set in, with ethanol production rates of up to 14 mmol of ethanol · g of biomass−1 · h−1at D = 0.40 h−1. A substantial fermentative capacity (assayed offline as ethanol production rate under anaerobic conditions) was found in cultures in which no ethanol was detectable (D < 0.28 h−1). This fermentative capacity increased with increasing dilution rates, from 10.0 mmol of ethanol · g of dry yeast biomass−1 · h−1 at D= 0.025 h−1 to 20.5 mmol of ethanol · g of dry yeast biomass−1 · h−1 atD = 0.28 h−1. At even higher dilution rates, the fermentative capacity showed only a small further increase, up to 22.0 mmol of ethanol · g of dry yeast biomass−1 · h−1 at D= 0.40 h−1. The activities of all glycolytic enzymes, pyruvate decarboxylase, and alcohol dehydrogenase were determined in cell extracts. Only the in vitro activities of pyruvate decarboxylase and phosphofructokinase showed a clear positive correlation with fermentative capacity. These enzymes are interesting targets for overexpression in attempts to improve the fermentative capacity of aerobic cultures grown at low specific growth rates.

scholarly journals Relationship between pH and Medium Dissolved Solids in Terms of Growth and Metabolism of Lactobacilli and Saccharomyces cerevisiae during Ethanol Production

2005 ◽  
Vol 71 (5) ◽  
pp. 2239-2243 ◽  
Author(s):  
Neelakantam V. Narendranath ◽  
Ronan Power
Keyword(s):  
Growth Rate ◽  
Lactic Acid ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Growth Rates ◽  
Specific Growth ◽  
Lactic Acid Production ◽  
Good Practice ◽  
Medium Ph ◽  
Dissolved Solids

ABSTRACT The specific growth rates of four species of lactobacilli decreased linearly with increases in the concentration of dissolved solids (sugars) in liquid growth medium. This was most likely due to the osmotic stress exerted by the sugars on the bacteria. The reduction in growth rates corresponded to decreased lactic acid production. Medium pH was another factor studied. As the medium pH decreased from 5.5 to 4.0, there was a reduction in the specific growth rate of lactobacilli and a corresponding decrease in the lactic acid produced. In contrast, medium pH did not have any significant effect on the specific growth rate of yeast at any particular concentration of dissolved solids in the medium. However, medium pH had a significant (P < 0.001) effect on ethanol production. A medium pH of 5.5 resulted in maximal ethanol production in all media with different concentrations of dissolved solids. When the data were analyzed as a 4 (pH levels) by 4 (concentrations of dissolved solids) factorial experiment, there was no synergistic effect (P > 0.2923) observed between pH of the medium and concentration of dissolved solids of the medium in reducing bacterial growth and metabolism. The data suggest that reduction of initial medium pH to 4.0 for the control of lactobacilli during ethanol production is not a good practice as there is a reduction (P < 0.001) in the ethanol produced by the yeast at pH 4.0. Setting the mash (medium) with ≥30% (wt/vol) dissolved solids at a pH of 5.0 to 5.5 will minimize the effects of bacterial contamination and maximize ethanol production by yeast.

scholarly journals Proteome allocations change linearly with specific growth rate of Saccharomyces cerevisiae under glucose-limitation

2021 ◽  
Author(s):  
Jianye Xia ◽  
Benjamin Sánchez ◽  
Yu Chen ◽  
Kate Campbell ◽  
Sergo Kasvandik ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Growth Rate ◽  
Specific Growth Rate ◽  
Growth Rates ◽  
Specific Growth ◽  
Cell Factory ◽  
Functional Protein ◽  
Wide Range ◽  
The Absolute ◽  
Specific Growth Rates

Abstract Saccharomyces cerevisiae is widely used as a cell factory and it is therefore important to understand how it organizes key functional parts when cultured under different conditions. Here we performed a multi-omics analysis of S. cerevisiae by culturing the strain under a wide range of specific growth rates using glucose as the sole limited nutrient. At these different conditions we measured the absolute transcriptome, the absolute proteome, the phosphproteome, and the metabolome. Most functional protein groups showed linear dependence on the cell specific growth rate. Proteins engaged with translation showed a perfect linear increase with the specific growth rate, while glycolysis and chaperone proteins showed a linear decrease at respiratory conditions. Glycolytic enzymes and chaperones, however, show decreased phosphorylation with increasing specific growth rates, resulting in an overall increased activity that is associated with increased flux through these pathways. Further analysis showed that proteome allocation was primarily determined at the transcriptome level. Finally, using enzyme constraint genome scale modeling we found that enzyme usage play an important role for controlling flux in amino acid biosynthesis.

scholarly journals Protein turnover forms one of the highest maintenance costs in Lactococcus lactis

Microbiology ◽  
2014 ◽  
Vol 160 (7) ◽  
pp. 1501-1512 ◽  
Author(s):  
Petri-Jaan Lahtvee ◽  
Andrus Seiman ◽  
Liisa Arike ◽  
Kaarel Adamberg ◽  
Raivo Vilu
Keyword(s):  
Growth Rate ◽  
Total Energy ◽  
Specific Growth Rate ◽  
Lactococcus Lactis ◽  
Protein Turnover ◽  
Biomass Yield ◽  
Specific Growth ◽  
High Energy ◽  
Turnover Rates ◽  
Maintenance Costs

Protein turnover plays an important role in cell metabolism by regulating metabolic fluxes. Furthermore, the energy costs for protein turnover have been estimated to account for up to a third of the total energy production during cell replication and hence may represent a major limiting factor in achieving either higher biomass or production yields. This work aimed to measure the specific growth rate (μ)-dependent abundance and turnover rate of individual proteins, estimate the ATP cost for protein production and turnover, and compare this with the total energy balance and other maintenance costs. The lactic acid bacteria model organism Lactococcus lactis was used to measure protein turnover rates at μ = 0.1 and 0.5 h−1 in chemostat experiments. Individual turnover rates were measured for ~75 % of the total proteome. On average, protein turnover increased by sevenfold with a fivefold increase in growth rate, whilst biomass yield increased by 35 %. The median turnover rates found were higher than the specific growth rate of the bacterium, which suggests relatively high energy consumption for protein turnover. We found that protein turnover costs alone account for 38 and 47 % of the total energy produced at μ = 0.1 and 0.5 h−1, respectively, and gene ontology groups Energy metabolism and Translation dominated synthesis costs at both growth rates studied. These results reflect the complexity of metabolic changes that occur in response to changes in environmental conditions, and signify the trade-off between biomass yield and the need to produce ATP for maintenance processes.

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