scholarly journals Comparison of Scheffersomyces stipitis strains CBS 5773 and CBS 6054 with regard to their xylose metabolism: implications for xylose fermentation

2012 ◽  
Vol 1 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Stefan Krahulec ◽  
Regina Kratzer ◽  
Karin Longus ◽  
Bernd Nidetzky
Keyword(s):  
Xylose Fermentation ◽  
Xylose Metabolism ◽  
Scheffersomyces Stipitis

scholarly journals Inhibition of alternative respiration system of Scheffersomyces stipitis and effect on glucose or xylose fermentation

2021 ◽  
Author(s):  
J A Granados-Arvizu ◽  
M Canizal-Garcia ◽  
L A Madrigal-Perez ◽  
J C González-Hernández ◽  
C Regalado-González
Keyword(s):  
Ethanol Production ◽  
Xylose Fermentation ◽  
Carbon Sources ◽  
Active Role ◽  
Glycolytic Flux ◽  
Alternative Respiration ◽  
Scheffersomyces Stipitis ◽  
Salicylhydroxamic Acid ◽  
Mild Reduction

Abstract Scheffersomyces stipitis is a Crabtree-negative pentose fermenting yeast, which shows a complex respiratory system involving a cytochrome and an alternative salicylhydroxamic acid (SHAM)-sensitive respiration mechanism that is poorly understood. This work aimed to investigate the role of the antimycin A (AA) sensitive respiration and SHAM-sensitive respiration in the metabolism of xylose and glucose by S. stipitis, upon different agitation conditions. Inhibition of the SHAM-sensitive respiration caused a significant (p < 0.05) decrease in glycolytic flux and oxygen consumption when using glucose and xylose under agitation conditions, but without agitation, only a mild reduction was observed. The combination of SHAM and AA abolished respiration, depleting the glycolytic flux using both carbon sources tested, leading to increased ethanol production of 21.05 g/L at 250 rpm for 0.5 M glucose, and 8.3 g/L ethanol using xylose. In contrast, inhibition of only the AA-sensitive respiration, caused increased ethanol production to 30 g/L using 0.5 M glucose at 250 rpm, and 11.3 g/L from 0.5 M xylose without agitation. Results showed that ethanol production can be induced by respiration inhibition, but the active role of SHAM-sensitive respiration should be considered to investigate better conditions to increase and optimize yields.

scholarly journals Novel Propagation Strategy of Saccharomyces cerevisiae for Enhanced Xylose Metabolism during Fermentation on Softwood Hydrolysate

Fermentation ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 288
Author(s):  
Andreea Cristina Dobrescu ◽  
Henrique César Teixeira Veras ◽  
Cristiano Varrone ◽  
Jan Dines Knudsen
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Second Generation ◽  
Xylose Fermentation ◽  
Carbon Sources ◽  
Fed Batch ◽  
Xylose Metabolism ◽  
Second Generation Bioethanol ◽  
Utilisation Rate ◽  
Shake Flasks ◽  
Production Strategy

An economically viable production of second-generation bioethanol by recombinant xylose-fermenting Saccharomyces cerevisiae requires higher xylose fermentation rates and improved glucose–xylose co-consumption. Moreover, xylose-fermenting S. cerevisiae recognises xylose as a non-fermentable rather than a fermentable carbon source, which might partly explain why xylose is not fermented into ethanol as efficiently as glucose. This study proposes propagating S. cerevisiae on non-fermentable carbon sources to enhance xylose metabolism during fermentation. When compared to yeast grown on sucrose, cells propagated on a mix of ethanol and glycerol in shake flasks showed up to 50% higher xylose utilisation rate (in a defined xylose medium) and a double maximum fermentation rate, together with an improved C5/C6 co-consumption (on an industrial softwood hydrolysate). Based on these results, an automated propagation protocol was developed, using a fed-batch approach and the respiratory quotient to guide the ethanol and glycerol-containing feed. This successfully produced 71.29 ± 0.91 g/L yeast with an average productivity of 1.03 ± 0.05 g/L/h. These empirical findings provide the basis for the design of a simple, yet effective yeast production strategy to be used in the second-generation bioethanol industry for increased fermentation efficiency.

scholarly journals Deletion ofFPS1, Encoding Aquaglyceroporin Fps1p, Improves Xylose Fermentation by Engineered Saccharomyces cerevisiae

2013 ◽  
Vol 79 (10) ◽  
pp. 3193-3201 ◽  
Author(s):  
Na Wei ◽  
Haiqing Xu ◽  
Soo Rin Kim ◽  
Yong-Su Jin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Xylose Fermentation ◽  
Plant Biomass ◽  
Ethanol Yield ◽  
Xylose Reductase ◽  
Enzymatic Reactions ◽  
Xylose Metabolism ◽  
Xylose Consumption ◽  
Content Type ◽  
Ethanol Yields

ABSTRACTAccumulation of xylitol in xylose fermentation with engineeredSaccharomyces cerevisiaepresents a major problem that hampers economically feasible production of biofuels from cellulosic plant biomass. In particular, substantial production of xylitol due to unbalanced redox cofactor usage by xylose reductase (XR) and xylitol dehydrogenase (XDH) leads to low yields of ethanol. While previous research focused on manipulating intracellular enzymatic reactions to improve xylose metabolism, this study demonstrated a new strategy to reduce xylitol formation and increase carbon flux toward target products by controlling the process of xylitol secretion. Using xylitol-producingS. cerevisiaestrains expressing XR only, we determined the role of aquaglyceroporin Fps1p in xylitol export by characterizing extracellular and intracellular xylitol. In addition, whenFPS1was deleted in a poorly xylose-fermenting strain with unbalanced XR and XDH activities, the xylitol yield was decreased by 71% and the ethanol yield was substantially increased by nearly four times. Experiments with our optimized xylose-fermenting strain also showed thatFPS1deletion reduced xylitol production by 21% to 30% and increased ethanol yields by 3% to 10% under various fermentation conditions. Deletion ofFPS1decreased the xylose consumption rate under anaerobic conditions, but the effect was not significant in fermentation at high cell density. Deletion ofFPS1resulted in higher intracellular xylitol concentrations but did not significantly change the intracellular NAD+/NADH ratio in xylose-fermenting strains. The results demonstrate that Fps1p is involved in xylitol export inS. cerevisiaeand present a new gene deletion target,FPS1, and a mechanism different from those previously reported to engineer yeast for improved xylose fermentation.

scholarly journals Parallel experimental evolution reveals a novel repressive control of GalP on xylose fermentation inEscherichia coli

2019 ◽  
Vol 116 (8) ◽  
pp. 2074-2086 ◽  
Author(s):  
Gavin Kurgan ◽  
Christian Sievert ◽  
Andrew Flores ◽  
Aidan Schneider ◽  
Thomas Billings ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Xylose Fermentation ◽  
Inescherichia Coli

scholarly journals Hemicellulosic Bioethanol Production from Fast-Growing Paulownia Biomass

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 173
Author(s):  
Elena Domínguez ◽  
Pablo G. del Río ◽  
Aloia Romaní ◽  
Gil Garrote ◽  
Lucília Domingues
Keyword(s):  
Ethanol Production ◽  
Ethanol Concentration ◽  
Ethanol Yield ◽  
Xylose Reductase ◽  
Energy Crop ◽  
Scheffersomyces Stipitis ◽  
Fractionation Process ◽  
Renewable Source ◽  
Fast Growing ◽  
Engineered Strain

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S0 of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach.

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