Evaluation of Brazilian ethanol production yeasts for maltose fermentation in media containing structurally complex nitrogen sources

Bioethanol is one of the most commonly used biofuels in transportation sector to reduce greenhouse gases. S. cerevisiae is the most employed yeast for ethanol production at industrial level though ethanol is produced by an array of other yeasts, bacteria, and fungi. This paper reviews the current and nonmolecular trends in ethanol production using S. cerevisiae. Ethanol has been produced from wide range of substrates such as molasses, starch based substrate, sweet sorghum cane extract, lignocellulose, and other wastes. The inhibitors in lignocellulosic hydrolysates can be reduced by repeated sequential fermentation, treatment with reducing agents and activated charcoal, overliming, anion exchanger, evaporation, enzymatic treatment with peroxidase and laccase, in situ detoxification by fermenting microbes, and different extraction methods. Coculturing S. cerevisiae with other yeasts or microbes is targeted to optimize ethanol production, shorten fermentation time, and reduce process cost. Immobilization of yeast cells has been considered as potential alternative for enhancing ethanol productivity, because immobilizing yeasts reduce risk of contamination, make the separation of cell mass from the bulk liquid easy, retain stability of cell activities, minimize production costs, enable biocatalyst recycling, reduce fermentation time, and protect the cells from inhibitors. The effects of growth variables of the yeast and supplementation of external nitrogen sources on ethanol optimization are also reviewed.

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Influence of Solid Loading Concentrations, Inoculums Size and Nitrogen Sources on Ethanol Production from Empty Fruit Bunches (EFB) Hydrolysate in Separate Hydrolysis and Fermentation (SHF)

Research Journal of Applied Sciences ◽

10.3923/rjasci.2011.310.319 ◽

2011 ◽

Vol 6 (5) ◽

pp. 310-319 ◽

Cited By ~ 3

Author(s):

Mohd Asyraf Kas ◽

Nasrin Abu Bakar ◽

Loh Soh Kheang ◽

Astimar Aziz

Keyword(s):

Ethanol Production ◽

Nitrogen Sources ◽

Solid Loading ◽

Empty Fruit Bunches ◽

Separate Hydrolysis And Fermentation

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Underlying Mechanism of Uncoupled Cell Growth and Ethanol Fermentation of Zymomonas mobilis using Different Nitrogen Sources

10.21203/rs.2.21812/v1 ◽

2020 ◽

Author(s):

Runxia Li ◽

Mingjie Jin ◽

Jun Du ◽

Shouwen Chen ◽

Shihui Yang

Keyword(s):

Cell Growth ◽

Metal Ions ◽

Ethanol Production ◽

Yeast Extract ◽

Stress Responses ◽

Ethanol Fermentation ◽

Culture Medium ◽

Nitrogen Sources ◽

Glucose Consumption ◽

Biochemical Production

Abstract Background: Microbial growth needs C, N, P, S as well as metal ions such as magnesium, which is a major cofactor for enzymes involved in various metabolic activities. Yeast extract is widely used as nitrogen supply as well as vitamins and growth factors to sustain microbial growth in the culture medium. Zymomonas mobilis is a model ethanologenic bacterium for ethanol production, and has been developing as a chassis for diverse biochemical production. Although yeast extract is routinely used to prepare rich medium (RM) for Z. mobilis, the glucose consumption and ethanol production of Z. mobilis in RM were not coupled with cell growth in some studies. Results: In this study, the effects of different nitrogen sources as well as the supplementation of additional nitrogen source into RM and minimum medium (MM) on cell growth and ethanol fermentation of Z. mobilis were investigated to understand the uncoupled cell growth and ethanol fermentation for efficient carbon utilization and optimal ethanol productivity of Z. mobilis. Our results indicated that nitrogen sources such as yeast extract from different companies affected cell growth, glucose utilization, and the corresponding ethanol production. We also quantified the concentrations of major ion elements in different organic nitrogen sources using the quantitative analytic approach of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), and demonstrated that metal ions such as magnesium in the media affected glucose consumption, cell growth, and ethanol fermentation. The effect of magnesium on gene expression was further investigated using RNA-Seq transcriptomics, and our result indicated that the lack of Mg2+ triggered stress responses while decreasing energy-consuming metabolism. Conclusions: Our work demonstrated that concentrations of metal ions such as magnesium and molybdenum in nitrogen sources are essential for vigorous cell growth, and the difference of Mg2+concentration in different yeast extract was one of the major factors affecting the coupling of cell growth and ethanol fermentation in Z. mobilis. We also revealed that genes responsive for Mg2+ deficiency in the medium were majorly related to stress responses and energy conservation. The importance of metal ions on cell growth and ethanol fermentation suggested that metal ions should become one of the parameters for monitoring the quality of commercial nitrogen sources and optimizing microbial culture medium for economic biochemical production.

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Effect of nitrogen sources on oxidoreductive enzymes and ethanol production during D-xylose fermentation by Candida shehatae

Canadian Journal of Microbiology ◽

10.1139/m92-043 ◽

1992 ◽

Vol 38 (3) ◽

pp. 258-260 ◽

Cited By ~ 12

Author(s):

Sanjay Palnitkar ◽

Anil Lachke

Keyword(s):

Ethanol Production ◽

Ammonium Sulphate ◽

Organic Nitrogen ◽

Xylose Fermentation ◽

Continuous Fermentation ◽

Nitrogen Sources ◽

Potassium Nitrate ◽

Yield Coefficient ◽

Xylose Utilization ◽

Candida Shehatae

The effect on D-xylose utilization and the corresponding xylitol and ethanol production by Candida shehatae (ATCC 22984) were examined with different nitrogen sources. These included organic (urea, asparagine, and peptone) and inorganic (ammonium chloride, ammonium nitrate, ammonium sulphate, and potassium nitrate) sources. Candida shehatae did not grow on potassium nitrate. Improved ethanol production (Y(p/s), yield coefficient (grams product/grams substrate), 0.34) was observed when organic nitrogen sources were used. Correspondingly, the xylitol production was also higher with organic sources. Ammonium sulphate showed the highest ethanol:xylitol ratio (11.0) among all the nitrogen sources tested. The ratio of NADH- to NADPH-linked D-xylose reductase (EC 1.1.1.21) appeared to be rate limiting during ethanologenesis of D-xylose. The levels of xylitol dehydrogenase (EC 1.1.1.9) were also elevated in the presence of organic nitrogen sources. These results may be useful in the optimization of alcohol production by C. shehatae during continuous fermentation of D-xylose. Key words: xylose fermentation, Candida shehatae, nitrogen source, oxidoreductive enzymes.

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Influence of nitrogen sources on ethanol production by Saccharomyces Spp in the presence of formic acid

Bayero Journal of Pure and Applied Sciences ◽

10.4314/bajopas.v11i1.1 ◽

2018 ◽

Vol 11 (1) ◽

pp. 1-7

Author(s):

C.E. Oshoma ◽

Henrietta O. Obueh

Keyword(s):

Formic Acid ◽

Ethanol Production ◽

Ammonium Sulphate ◽

Nitrogen Sources ◽

Fermentation Medium ◽

Cell Number ◽

Inhibitory Compounds ◽

Significant Difference ◽

Maximum Cell ◽

Assimilable Nitrogen

Formic acid is one of the major inhibitory compounds present in hydrolysates derived from lignocellulosic materials, the presence of which can significantly hamper the efficiency of converting available sugars in the hydrolysates to bioethanol. The influence of different nitrogen sources supplemented media on bioethanol fermentation with Saccharomyces spp in the presence of formic acid was studied. The addition of ammonium sulphate and urea significantly increased cell number, glucose utilization, ethanol and glycerol production when compared with control media. It was observed that supplementation with nitrogen sources contributed assimilable nitrogen for the yeast strains growth when stressed with formic acid. The best concentration of nitrogen to be utilized by yeast was found to be 0.80 gN/L. The maximum cell numbers were 8.17± 0.23x 107 and 8.68± 0.16x 107 cells/mL for ammonium sulphate medium while control had the least of 4.00± 0.20x 107 and 4.97± 0.08x 107 cells/mL for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. Ethanol accumulation increased with the consumption of glucose. The maximum ethanol production were 20.49 ± 1.24 and 19.74± 0.89 g/L using ammonium sulphate for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. There was significant difference in ethanol production when the nitrogen sources were compared with the control medium (p< 0.05). The highest glycerol produced were 2.21 ± 0.04 and 3.11± 0.05 g/L using ammonium sulphate for S. cerevisiae NCYC2592 and S. arboricolus 2.3319 respectively. The conclusion was that yeast tolerance to formic acid and ethanol production could be achieved when fermentation medium is supplemented with nitrogen sources specifically ammonium sulphate.Keywords: Lignocellulose, inhibitors, Saccharomyces, fermentation, yeast, biofuel

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