scholarly journals Simultaneous saccharification and co-fermentation with a thermotolerant Saccharomyces cerevisiae to produce ethanol from sugarcane bagasse under high temperature conditions

BioResources ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. 1358-1372
Author(s):  
Wei-Lin Tu ◽  
Tien-Yang Ma ◽  
Chung-Mao Ou ◽  
Gia-Luen Guo ◽  
Yu Chao
Keyword(s):  
Saccharomyces Cerevisiae ◽  
High Temperature ◽  
Ethanol Production ◽  
Sugarcane Bagasse ◽  
Ethanol Yield ◽  
Xylose Utilization ◽  
Inhibitor Tolerance ◽  
Temperature Conditions ◽  
Xylose Uptake ◽  
Simultaneous Saccharification

Lignocellulosic ethanol production at high temperature offers advantages such as the decrease of contamination risk and cooling cost. Recombinant xylose-fermenting Saccharomyces cerevisiae has been considered a promising strain for ethanol production from lignocellulose for its high inhibitor tolerance and superior capability to ferment glucose and xylose into ethanol. To improve the ethanolic fermentation by xylose at high temperature, the strain YY5A was subjected to the ethyl methanesulfonate (EMS) mutagenesis. A mutant strain T5 was selected from the EMS-treated cultures to produce ethanol. However, the xylose uptake by T5 was severely inhibited by the high ethanol concentration during the co-fermentation in defined YPDX medium at 40 °C. In this study, the simultaneous saccharification and co-fermentation (SSCF) and the separate hydrolysis and co-fermentation (SHCF) processes of sugarcane bagasse were assessed to solve this problem. The xylose utilization by T5 was remarkably improved using the SSCF process compared to the SHCF process. For the SHCF and SSCF processes, 48% and 99% of the xylose in the hydrolysate was consumed at 40 °C, respectively. The ethanol yield was enhanced by the SSCF process. The ethanol production can reach to 36.0 g/L using this process under high-temperature conditions.

scholarly journals Robustness and Ethanol Production of Industrial Strains of Saccharomyces cerevisiae Using Different Sugarcane Bagasse Hydrolysates

2019 ◽  
Vol 7 (1) ◽  
pp. 23 ◽  
Author(s):  
Vanessa S. Teixeira ◽  
Suéllen P. H. Azambuja ◽  
Priscila H. Carvalho ◽  
Fátima A. A. Costa ◽  
Patricia R. Kitaka ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ethanol Production ◽  
Sugarcane Bagasse ◽  
Ethanol Yield ◽  
Raw Materials ◽  
Fermentation Inhibitors ◽  
Severe Condition ◽  
Inhibitor Tolerance ◽  
Industrial Strains ◽  
Materials Used

Sugarcane bagasse is one of the main lignocellulosic raw materials used for the production of second-generation ethanol. Technological studies on fermentation processes have focused on the search for and development of more robust microorganisms that are able to produce bioethanol efficiently and are resistant to the main fermentation inhibitors. The purpose of this study was to evaluate the robustness and ethanol production of industrial strains of Saccharomyces cerevisiae using acid, alkaline, and enzymatic sugarcane bagasse hydrolysates. Hydrolysis was carried out to release fermentable sugars from sugarcane bagasse. Fermentations were performed in shake flasks containing sugarcane hydrolysates supplemented with 150 g L−1 glucose to evaluate the kinetic parameters of the reaction. Inhibitor tolerance was evaluated by incubating cells with different concentrations of inhibitors in 96-well plates. The biomass yield on substrate, ethanol yield on substrate, and ethanol productivity of the six strains were higher in 0.5% acid, 0.5% alkaline, and enzymatic hydrolysates (i.e., under milder conditions). The SA-1 (Santa Adélia-1) strain had a better performance in comparison with the other strains for its ability to produce ethanol in a very severe condition (7% acid hydrolysis) and for its robustness in growing at several inhibitor concentrations.

scholarly journals Directed Evolution of Xylose Isomerase for Improved Xylose Catabolism and Fermentation in the Yeast Saccharomyces cerevisiae

2012 ◽  
Vol 78 (16) ◽  
pp. 5708-5716 ◽  
Author(s):  
Sun-Mi Lee ◽  
Taylor Jellison ◽  
Hal S. Alper
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ethanol Production ◽  
Directed Evolution ◽  
Ethanol Yield ◽  
Xylose Isomerase ◽  
Mutant Enzyme ◽  
Xylose Utilization ◽  
Xylose Consumption ◽  
Content Type ◽  
Consumption Rates

ABSTRACTThe heterologous expression of a highly functional xylose isomerase pathway inSaccharomyces cerevisiaewould have significant advantages for ethanol yield, since the pathway bypasses cofactor requirements found in the traditionally used oxidoreductase pathways. However, nearly all reported xylose isomerase-based pathways inS. cerevisiaesuffer from poor ethanol productivity, low xylose consumption rates, and poor cell growth compared with an oxidoreductase pathway and, additionally, often require adaptive strain evolution. Here, we report on the directed evolution of thePiromycessp. xylose isomerase (encoded byxylA) for use in yeast. After three rounds of mutagenesis and growth-based screening, we isolated a variant containing six mutations (E15D, E114G, E129D, T142S, A177T, and V433I) that exhibited a 77% increase in enzymatic activity. When expressed in a minimally engineered yeast host containing agre3knockout andtal1andXKS1overexpression, the strain expressing this mutant enzyme improved its aerobic growth rate by 61-fold and both ethanol production and xylose consumption rates by nearly 8-fold. Moreover, the mutant enzyme enabled ethanol production by these yeasts under oxygen-limited fermentation conditions, unlike the wild-type enzyme. Under microaerobic conditions, the ethanol production rates of the strain expressing the mutant xylose isomerase were considerably higher than previously reported values for yeast harboring a xylose isomerase pathway and were also comparable to those of the strains harboring an oxidoreductase pathway. Consequently, this study shows the potential to evolve a xylose isomerase pathway for more efficient xylose utilization.

Proper ultrasound treatment increases ethanol production from simultaneous saccharification and fermentation of sugarcane bagasse

RSC Advances ◽  
2016 ◽  
Vol 6 (94) ◽  
pp. 91409-91419 ◽  
Author(s):  
Rajendran Velmurugan ◽  
Aran Incharoensakdi
Keyword(s):  
Ethanol Production ◽  
Sugarcane Bagasse ◽  
Simultaneous Saccharification And Fermentation ◽  
Ethanol Yield ◽  
Ultrasound Treatment ◽  
Fermentation Processes ◽  
Cellulase Complex ◽  
Simultaneous Saccharification

To improve the saccharification and fermentation processes, proper ultrasound was applied which resulted in the presence of cellulase complex with improved β-glucosidase ratio leading to enhanced overall ethanol yield.

Bio-ethanol production from Elephant grass using co-cultures of Aspergillus niger and Saccharomyces cerevisiae in simultaneous saccharification and fermentation

2013 ◽  
Vol 3 (4) ◽  
pp. 152-157
Author(s):  
T. C. Agbodike ◽  
S. A. Ado ◽  
I. O. Abdullahi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Aspergillus Niger ◽  
Ethanol Production ◽  
Simultaneous Saccharification And Fermentation ◽  
Ethanol Yield ◽  
Pennisetum Purpureum ◽  
Plant Sample ◽  
Agitation Rate ◽  
Elephant Grass ◽  
Simultaneous Saccharification

Elephant grass (Pennisetum purpureum) was evaluated for its ethanol production potential using co-cultures of Aspergillus niger and Saccharomyces cerevisiae. Proximate and lignocellulose analysis carried out on the plant sample showed that it had crude fibre, lignin, hemicellulose and cellulose contents of 31.5%, 26.78%, 18.76% and 34.16% respectively. A. niger strain (AN-15) used for the simultaneous saccharification and fermentation (SSF) of the plant sample was isolated from soil and selected upon subsequent screening because it gave highest yield of cellulase enzyme (0.1792 IU/ml/min). S. cerevisiae strain (PW-4) used for the SSF was isolated from palm wine and selected upon subsequent screening after showing ability to assimilate more sugars compared to other isolates. Fermentation of plant sample was carried out at different substrate concentrations ranging from 2-10% and highest ethanol yield (1.68g/100ml) was observed at 6% substrate concentration though lesser than that observed for glucose at same concentration (8.38g/100ml). Optimization of culture parameters for ethanol production showed maximum ethanol yield at pH 5, 35oC and agitation rate of 300 rpm.

scholarly journals Effects of Ultrasound on Fermentation of Glucose to Ethanol by Saccharomyces cerevisiae

Fermentation ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 16 ◽  
Author(s):  
Luis Huezo ◽  
Ajay Shah ◽  
Frederick Michel
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mass Transfer ◽  
Glucose Uptake ◽  
Ethanol Production ◽  
Ethanol Yield ◽  
Biofuel Production ◽  
Inhibitory Effects ◽  
Negative Effects ◽  
Intraparticle Mass Transfer ◽  
Improve Mass Transfer

Previous studies have shown that pretreatment of corn slurries using ultrasound improves starch release and ethanol yield during biofuel production. However, studies on its effects on the mass transfer of substrates and products during fermentation have shown that it can have both beneficial and inhibitory effects. In this study, the effects of ultrasound on mass transfer limitations during fermentation were examined. Calculation of the external and intraparticle observable moduli under a range of conditions indicate that no external or intraparticle mass transfer limitations should exist for the mass transfer of glucose, ethanol, or carbon dioxide. Fermentations of glucose to ethanol using Saccharomyces cerevisiae were conducted at different ultrasound intensities to examine its effects on glucose uptake, ethanol production, and yeast population and viability. Four treatments were compared: direct ultrasound at intensities of 23 and 32 W/L, indirect ultrasound (1.4 W/L), and no-ultrasound. Direct and indirect ultrasound had negative effects on yeast performance and viability, and reduced the rates of glucose uptake and ethanol production. These results indicate that ultrasound during fermentation, at the levels applied, is inhibitory and not expected to improve mass transfer limitations.

scholarly journals Recombinant Diploid Saccharomyces cerevisiae Strain Development for Rapid Glucose and Xylose Co-Fermentation

Fermentation ◽  
2018 ◽  
Vol 4 (3) ◽  
pp. 59 ◽  
Author(s):  
Tingting Liu ◽  
Shuangcheng Huang ◽  
Anli Geng
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Alcoholic Fermentation ◽  
Ethanol Yield ◽  
Xylose Isomerase ◽  
Cost Effective ◽  
Xylose Utilization ◽  
Yeast Strains ◽  
Multiple Copies ◽  
Biomass Sugars ◽  
Sugar Conversion

Cost-effective production of cellulosic ethanol requires robust microorganisms for rapid co-fermentation of glucose and xylose. This study aims to develop a recombinant diploid xylose-fermenting Saccharomyces cerevisiae strain for efficient conversion of lignocellulosic biomass sugars to ethanol. Episomal plasmids harboring codon-optimized Piromyces sp. E2 xylose isomerase (PirXylA) and Orpinomyces sp. ukk1 xylose (OrpXylA) genes were constructed and transformed into S. cerevisiae. The strain harboring plasmids with tandem PirXylA was favorable for xylose utilization when xylose was used as the sole carbon source, while the strain harboring plasmids with tandem OrpXylA was beneficial for glucose and xylose cofermentation. PirXylA and OrpXylA genes were also individually integrated into the genome of yeast strains in multiple copies. Such integration was beneficial for xylose alcoholic fermentation. The respiration-deficient strain carrying episomal or integrated OrpXylA genes exhibited the best performance for glucose and xylose co-fermentation. This was partly attributed to the high expression levels and activities of xylose isomerase. Mating a respiration-efficient strain carrying the integrated PirXylA gene with a respiration-deficient strain harboring integrated OrpXylA generated a diploid recombinant xylose-fermenting yeast strain STXQ with enhanced cell growth and xylose fermentation. Co-fermentation of 162 g L−1 glucose and 95 g L−1 xylose generated 120.6 g L−1 ethanol in 23 h, with sugar conversion higher than 99%, ethanol yield of 0.47 g g−1, and ethanol productivity of 5.26 g L−1·h−1.

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