scholarly journals Cellulosic ethanol production by consortia of Scheffersomyces stipitis and engineered Zymomonas mobilis

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Lingling Sun ◽  
Bo Wu ◽  
Zengqin Zhang ◽  
Jing Yan ◽  
Panting Liu ◽  
...  
Keyword(s):  
Ethanol Production ◽  
Zymomonas Mobilis ◽  
Carbon Dioxide Emission ◽  
Strain Improvement ◽  
Superior Performance ◽  
Pcr Analysis ◽  
Lignocellulosic Ethanol ◽  
Fermentation Performance ◽  
Scheffersomyces Stipitis ◽  
Xylose Consumption

Abstract Background As one of the clean and sustainable energies, lignocellulosic ethanol has achieved much attention around the world. The production of lignocellulosic ethanol does not compete with people for food, while the consumption of ethanol could contribute to the carbon dioxide emission reduction. However, the simultaneous transformation of glucose and xylose to ethanol is one of the key technologies for attaining cost-efficient lignocellulosic ethanol production at an industrial scale. Genetic modification of strains and constructing consortia were two approaches to resolve this issue. Compared with strain improvement, the synergistic interaction of consortia in metabolic pathways should be more useful than using each one separately. Results In this study, the consortia consisting of suspended Scheffersomyces stipitis CICC1960 and Zymomonas mobilis 8b were cultivated to successfully depress carbon catabolite repression (CCR) in artificially simulated 80G40XRM. With this strategy, a 5.52% more xylose consumption and a 6.52% higher ethanol titer were achieved by the consortium, in which the inoculation ratio between S. stipitis and Z. mobilis was 1:3, compared with the Z. mobilis 8b mono-fermentation. Subsequently, one copy of the xylose metabolic genes was inserted into the Z. mobilis 8b genome to construct Z. mobilis FR2, leading to the xylose final-consumption amount and ethanol titer improvement by 15.36% and 6.81%, respectively. Finally, various corn stover hydrolysates with different sugar concentrations (glucose and xylose 60, 90, 120 g/L), were used to evaluate the fermentation performance of the consortium consisting of S. stipitis CICC1960 and Z. mobilis FR2. Fermentation results showed that a 1.56–4.59% higher ethanol titer was achieved by the consortium compared with the Z. mobilis FR2 mono-fermentation, and a 46.12–102.14% higher ethanol titer was observed in the consortium fermentation when compared with the S. stipitis CICC1960 mono-fermentation. Furthermore, qRT-PCR analysis of xylose/glucose transporter and other genes responsible for CCR explained the reason why the initial ratio inoculation of 1:3 in artificially simulated 80G40XRM had the best fermentation performance in the consortium. Conclusions The fermentation strategy used in this study, i.e., using a genetically modified consortium, had a superior performance in ethanol production, as compared with the S. stipitis CICC1960 mono-fermentation and the Z. mobilis FR2 mono-fermentation alone. This result showed that this strategy has potential for future lignocellulosic ethanol production.

scholarly journals Cellulosic Ethanol Production by Engineered Consortia of Scheffersomyces Stipitis and Zymomonas Mobilis

2021 ◽  
Author(s):  
Lingling Sun ◽  
Bo Wu ◽  
Zengqin Zhang ◽  
Jing Yan ◽  
Panting Liu ◽  
...  
Keyword(s):  
Ethanol Production ◽  
Zymomonas Mobilis ◽  
Carbon Dioxide Emission ◽  
Superior Performance ◽  
Lignocellulosic Ethanol ◽  
Scheffersomyces Stipitis ◽  
Xylose Consumption ◽  
Metabolic Genes ◽  
Fermentation Strategy ◽  
Cost Efficient

Abstract Background: As one of the clean and sustainable energies, lignocellulosic ethanol has achieved much attention around the world. The production of lignocellulosic ethanol does not compete with people for food, while the consumption of ethanol could contribute to the carbon dioxide emission reduction. Two of the conditions that are needed to attain cost-efficient lignocellulosic ethanol production at an industrial scale are the simultaneous transformation of glucose and xylose to ethanol and a highly efficient ethanol fermentation process. Results: In this study, the consortia consisting of suspended Scheffersomyces stipitis CICC1960 and Zymomonas mobilis 8b were cultivated to successfully depress carbon catabolite repression (CCR) in 80G40XRM. With this strategy, a 5.52% more xylose consumption and a 6.52% higher ethanol titer were achieved by the consortium, in which the inoculation ratio between S. stipitis and Z. mobilis was 1:3, at the end of fermentation compared with the Z. mobilis 8b mono-fermentation. Subsequently, one copy of the xylose metabolic genes was inserted into the Z. mobilis 8b genome to construct Z. mobilis FR2, leading to the xylose final-consumption amount and ethanol titer improvement by 15.36% and 6.81%, respectively. Finally, various concentrations of corn stover hydrolysates, in which the sum of glucose and xylose concentrations in the hydrolysates were 60, 90, and 120 g/L respectively, were used to evaluate the fermentation performance of the consortium consisting of S. stipitis CICC1960 and Z. mobilis FR2. Fermentation results showed that a 1.56% - 4.59% higher ethanol titer was achieved by the consortium compared with the Z. mobilis FR2 mono-fermentation, and a 46.12% - 102.14% higher ethanol titer was observed in the consortium fermentation when compared with the S. stipitis CICC1960 mono-fermentation. Conclusions: The fermentation strategy used in this study, i.e., using a genetically modified consortium, had a superior performance in ethanol production, as compared with the S. stipitis CICC1960 mono-fermentation and the Z. mobilis FR2 mono-fermentation alone. Thus, this strategy has potential for future lignocellulosic ethanol production.

Two-reactor, continuous culture fermentation for fuel ethanol production from lignocellulosic acid hydrolysate using Zymomonas mobilis and Scheffersomyces stipitis

RSC Advances ◽  
2014 ◽  
Vol 4 (69) ◽  
pp. 36412-36418 ◽  
Author(s):  
Gaurav Chaudhary ◽  
Sanjoy Ghosh
Keyword(s):  
Ethanol Production ◽  
Continuous Culture ◽  
Zymomonas Mobilis ◽  
Fuel Ethanol ◽  
Ethanol Productivity ◽  
Scheffersomyces Stipitis ◽  
Acid Hydrolysate

Multistage ethanol production from lignocellulosic acid hydrolysate using two different microorganisms in two reactors enhances the utilization of all sugars (pentose and hexose), with higher ethanol productivity.

Metabolic and evolutionary engineering of diploid yeast for the production of first-and second-generation ethanol

2020 ◽  
Author(s):  
Yang Sun ◽  
Qian Xue ◽  
Junyan Hou ◽  
Meilin Kong ◽  
Xiaowei Li ◽  
...  
Keyword(s):  
Ethanol Production ◽  
Gene Cluster ◽  
Second Generation ◽  
Corn Starch ◽  
Xylose Fermentation ◽  
Strain Improvement ◽  
Limiting Factors ◽  
Evolutionary Engineering ◽  
Diploid Strain ◽  
Xylose Consumption

Abstract Background: Saccharomyces cerevisiae has been widely used in the fermentation of plant-derived sugars to produce ethanol, called first-generation (1G) bioethanol, but made an impact on global food markets. Significant efforts have been therefore to employ non-food lignocellulosic feedstocks for bioethanol production, known as second-generation (2G) bioethanol. However, S. cerevisiae cannot naturally utilize xylose, a major component in lignocellulosic hydrolysates, and it has low tolerance to common carboxylic acid inhibitors present in lignocellulosic hydrolyzates. Metabolic engineering and evolutionary engineering have shown great power in strain improvement, which were also adopted here to solve these limiting factors in developing 2G bioethanol.Results: An efficient expression of a six-gene cluster, including XYL1/XYL2/XKS1/TAL1/PYK1/MGT05196, was achieved in the evolved S. cerevisiae diploid strain A21Z, showing the ability to use mixed glucose and xylose. The engineered strain A21Z expressing the six-gene cluster displayed a high xylose consumption after 96 h, reaching 90.7% of the theoretical yield in ethanol production. To investigate its industrial characteristics, A31Z was obtained by direct evolution of A21Z under the treatment of industrial hydrolysate from wheat straw. Under different fermentation conditions with 1G and 2G feedstock candidates, A31Z showed a markedly improved xylose fermentation performance. A31Z could produce more ethanol and less glycerol compared to the control Angel from corn starch during 120 h, with a final ethanol production at 122.32 g/L. The ability to produce higher ethanol production was also found under the fermentation using carbon source from hydrolysis of Dried Distillers Grains with Solubles (DDGS) or whole corn.Conclusions: Here, we report an effective strategy to improve xylose fermentation with an evolutionary engineering in the industrial S. cerevisiae diploid strain A31Z. This study demonstrated that a constructed A31Z has the higher xylose consumption and efficient ethanol production in mixed glucose and xylose with acetate. A31Z also gave a good ethanol production in 1G and 2G industrial feedstocks, indicating its significant contribution in the transition stage from the 1st generation to the 2nd generation bioethanol.

Strain improvement of native Saccharomyces cerevisiae LN ITCC 8246 strain through protoplast fusion to enhance its xylose uptake

2021 ◽  
Author(s):  
Shalley Sharma ◽  
Chandrika Ghoshal ◽  
Anju Arora ◽  
Wara Samar ◽  
Lata Nain ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protoplast Fusion ◽  
Strain Improvement ◽  
Pichia Stipitis ◽  
Pcr Analysis ◽  
Rt Pcr ◽  
Xylose Metabolism ◽  
Xylose Consumption ◽  
Xylose Uptake ◽  
Electric Impulse

Abstract Co-utilization of xylose and glucose and subsequent fermentation using Saccharomyces cerevisiae could enhance ethanol productivity. Directed engineering approaches have met with limited success due to interconnectivity of xylose metabolism with other intrinsic, hidden pathways. Therefore, random approaches like protoplast fusion were used to reprogram unidentified mechanisms. Saccharomyces cerevisiae LN, the best hexose fermenter, was fused with xylose fermenting Pichia stipitis NCIM 3498. Protoplasts prepared using glucanex were fused under electric impulse and fusants were selected using 10% ethanol and cycloheximide (50 ppm) markers. Two fusants, 1a.23 and 1a.30 showing fast growth on xylose and tolerance to 10% ethanol, were selected. Higher extracellular protein expression observed in fusants as compared to parents was corroborated by higher number of bands resolved by twodimensional analysis. Overexpression of XYL1, XYL2, XKS and XUT4 in fusants as compared to S. cerevisiae LN as observed by RT-PCR analysis was substantiated by higher specific activities of XR, XDH and XKS enzymes in fusants. During lignocellulosic hydrolysate fermentation, fusants could utilize glucose faster than the parent P. stipitis NCIM 3498 and xylose consumption in fusants was higher than S. cerevisiae LN.

scholarly journals The Quorum Sensing Auto-Inducer 2 (AI-2) Stimulates Nitrogen Fixation and Favors Ethanol Production over Biomass Accumulation in Zymomonas mobilis

2021 ◽  
Vol 22 (11) ◽  
pp. 5628
Author(s):  
Valquíria Campos Alencar ◽  
Juliana de Fátima dos Santos Silva ◽  
Renata Ozelami Vilas Boas ◽  
Vinícius Manganaro Farnézio ◽  
Yara N. L. F. de Maria ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Quorum Sensing ◽  
Ethanol Production ◽  
N2 Fixation ◽  
Energy Demand ◽  
Zymomonas Mobilis ◽  
Biomass Accumulation ◽  
High Energy ◽  
Gram Negative ◽  
Expression Of Genes

Autoinducer 2 (or AI-2) is one of the molecules used by bacteria to trigger the Quorum Sensing (QS) response, which activates expression of genes involved in a series of alternative mechanisms, when cells reach high population densities (including bioluminescence, motility, biofilm formation, stress resistance, and production of public goods, or pathogenicity factors, among others). Contrary to most autoinducers, AI-2 can induce QS responses in both Gram-negative and Gram-positive bacteria, and has been suggested to constitute a trans-specific system of bacterial communication, capable of affecting even bacteria that cannot produce this autoinducer. In this work, we demonstrate that the ethanologenic Gram-negative bacterium Zymomonas mobilis (a non-AI-2 producer) responds to exogenous AI-2 by modulating expression of genes involved in mechanisms typically associated with QS in other bacteria, such as motility, DNA repair, and nitrogen fixation. Interestingly, the metabolism of AI-2-induced Z. mobilis cells seems to favor ethanol production over biomass accumulation, probably as an adaptation to the high-energy demand of N2 fixation. This opens the possibility of employing AI-2 during the industrial production of second-generation ethanol, as a way to boost N2 fixation by these bacteria, which could reduce costs associated with the use of nitrogen-based fertilizers, without compromising ethanol production in industrial plants.

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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