scholarly journals Identification of the major fermentation inhibitors of recombinant 2G yeasts in diverse lignocellulose hydrolysates

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Gert Vanmarcke ◽  
Mekonnen M. Demeke ◽  
Maria R. Foulquié-Moreno ◽  
Johan M. Thevelein
Keyword(s):  
Second Generation ◽  
Industrial Process ◽  
Superior Performance ◽  
Fermentation Inhibitors ◽  
Inhibitor Tolerance ◽  
Xylose Consumption ◽  
Process Economics ◽  
Partial Inhibition ◽  
Second Generation Bioethanol ◽  
Lignocellulose Hydrolysates

Abstract Background Presence of inhibitory chemicals in lignocellulose hydrolysates is a major hurdle for production of second-generation bioethanol. Especially cheaper pre-treatment methods that ensure an economical viable production process generate high levels of these inhibitory chemicals. The effect of several of these inhibitors has been extensively studied with non-xylose-fermenting laboratory strains, in synthetic media, and usually as single inhibitors, or with inhibitor concentrations much higher than those found in lignocellulose hydrolysates. However, the relevance of individual inhibitors in inhibitor-rich lignocellulose hydrolysates has remained unclear. Results The relative importance for inhibition of ethanol fermentation by two industrial second-generation yeast strains in five lignocellulose hydrolysates, from bagasse, corn cobs and spruce, has now been investigated by spiking higher concentrations of each compound in a concentration range relevant for industrial hydrolysates. The strongest inhibition was observed with industrially relevant concentrations of furfural causing partial inhibition of both D-glucose and D-xylose consumption. Addition of 3 or 6 g/L furfural strongly reduced the ethanol titer obtained with strain MD4 in all hydrolysates evaluated, in a range of 34 to 51% and of 77 to 86%, respectively. This was followed by 5-hydroxymethylfurfural, acetic acid and formic acid, for which in general, industrially relevant concentrations caused partial inhibition of D-xylose fermentation. On the other hand, spiking with levulinic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid or vanillin caused little inhibition compared to unspiked hydrolysate. The further evolved MD4 strain generally showed superior performance compared to the previously developed strain GSE16-T18. Conclusion The results highlight the importance of individual inhibitor evaluation in a medium containing a genuine mix of inhibitors as well as the ethanol that is produced by the fermentation. They also highlight the potential of increasing yeast inhibitor tolerance for improving industrial process economics.

scholarly journals Flocculation Causes Inhibitor Tolerance in Saccharomyces cerevisiae for Second-Generation Bioethanol Production

2014 ◽  
Vol 80 (22) ◽  
pp. 6908-6918 ◽  
Author(s):  
Johan O. Westman ◽  
Valeria Mapelli ◽  
Mohammad J. Taherzadeh ◽  
Carl Johan Franzén
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Second Generation ◽  
Raw Materials ◽  
Defined Medium ◽  
Bioethanol Production ◽  
Dilute Acid ◽  
Fermentation Inhibitors ◽  
Inhibitor Tolerance ◽  
Content Type ◽  
Second Generation Bioethanol

ABSTRACTYeast has long been considered the microorganism of choice for second-generation bioethanol production due to its fermentative capacity and ethanol tolerance. However, tolerance toward inhibitors derived from lignocellulosic materials is still an issue. Flocculating yeast strains often perform relatively well in inhibitory media, but inhibitor tolerance has never been clearly linked to the actual flocculation abilityper se. In this study, variants of the flocculation geneFLO1were transformed into the genome of the nonflocculating laboratory yeast strainSaccharomyces cerevisiaeCEN.PK 113-7D. Three mutants with distinct differences in flocculation properties were isolated and characterized. The degree of flocculation and hydrophobicity of the cells were correlated to the length of the gene variant. The effect of different strength of flocculation on the fermentation performance of the strains was studied in defined medium with or without fermentation inhibitors, as well as in media based on dilute acid spruce hydrolysate. Strong flocculation aided against the readily convertible inhibitor furfural but not against less convertible inhibitors such as carboxylic acids. During fermentation of dilute acid spruce hydrolysate, the most strongly flocculating mutant with dense cell flocs showed significantly faster sugar consumption. The modified strain with the weakest flocculation showed a hexose consumption profile similar to the untransformed strain. These findings may explain why flocculation has evolved as a stress response and can find application in fermentation-based biorefinery processes on lignocellulosic raw materials.

scholarly journals Biodegradation of 5-(Hydroxymethyl)-furfural and Furan Derivatives

Proceedings ◽  
2018 ◽  
Vol 2 (20) ◽  
pp. 1283 ◽  
Author(s):  
María Isabel Igeño ◽  
Rubén Sánchez-Clemente ◽  
Ana G. Población ◽  
M. Isabel Guijo ◽  
Faustino Merchán ◽  
...  
Keyword(s):  
Furan Ring ◽  
Degradation Products ◽  
Chemical Compounds ◽  
Aldehyde Group ◽  
Bacterial Strains ◽  
Fermentation Inhibitors ◽  
Furan Derivatives ◽  
Hydroxymethyl Furfural ◽  
Common Thread ◽  
Lignocellulose Hydrolysates

Furfural and 5-hydroxymethylfurfural (HMF) are degradation products of lignocellulose during pretreatment operations. Furfural compounds are a group of chemical compounds whose common thread is an aldehyde group attached to a furan ring, and they constitute a problem for the development of second-generation biofuels because they act as fermentation inhibitors of the lignocellulose hydrolysates. Up to date, very few bacteria have been described to be able to eliminate them. The objective of this work was to isolate and characterize bacterial strains able to use, as the sole carbon source, 5-(hydroxymethyl)-furfural (HMF) and furan derivatives.

Ionic Liquid 1-Butyl-3-Methylimidazolium Chloride/FeCl3 Pretreatment of Sugarcane Residue for Second Generation Bioethanol Production

2013 ◽  
Vol 275-277 ◽  
pp. 1662-1665 ◽  
Author(s):  
Qiang Li ◽  
Juan Juan Fei ◽  
Xu Ding Gu ◽  
Geng Sheng Ji ◽  
Yang Liu ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Enzymatic Hydrolysis ◽  
Low Temperature ◽  
Second Generation ◽  
Reducing Sugars ◽  
Enzymatic Saccharification ◽  
Cellulosic Biomass ◽  
Candida Shehatae ◽  
Second Generation Bioethanol ◽  
Temperature Pretreatment

This study aims to establish a natural cellulosic biomass pretreatment process using ionic liquid (IL) for efficient enzymatic hydrolysis and second generation bioethanol. The IL 1-Butyl-3-methylimidazolium Chloride/FeCl3 ([Bmim]Cl/FeCl3) was selected in view of its low temperature pretreatment ability and the potential of accelerating enzymatic hydrolysis, and it could be recyclable. The yield of reducing sugars from sugarcane residue pretreated with this IL at 80 oC for 1 h reached 46.8% after being enzymatically hydrolyzed for 24 h. Sugarcane residue regenerated were hydrolyzed more easily than that treated with water. The fermentability of the hydrolyzates, obtained after enzymatic saccharification of the regenerated sugarcane residue, was transformed into bioethanol using Candida shehatae. This microbe could absorb glucose and xylose efficiently, and the ethanol production was 0.38 g/g glucose within 30 h fermentation. In conclusion, the metal ionic liquid pretreatment in low temperature shows promise as pretreatment solvent for natural biomass.

scholarly journals Exploring grape marc as trove for new thermotolerant and inhibitor-tolerant Saccharomyces cerevisiae strains for second-generation bioethanol production

2013 ◽  
Vol 6 (1) ◽  
pp. 168 ◽  
Author(s):  
Lorenzo Favaro ◽  
Marina Basaglia ◽  
Alberto Trento ◽  
Eugéne Van Rensburg ◽  
Maria García-Aparicio ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Second Generation ◽  
Bioethanol Production ◽  
Grape Marc ◽  
Second Generation Bioethanol

scholarly journals Sustainable Second-Generation Bioethanol Production from Enzymatically Hydrolyzed Domestic Food Waste Using Pichia anomala as Biocatalyst

2020 ◽  
Vol 13 (1) ◽  
pp. 259
Author(s):  
Ioanna Ntaikou ◽  
Georgia Antonopoulou ◽  
Gerasimos Lyberatos
Keyword(s):  
Food Waste ◽  
Second Generation ◽  
Scale Up ◽  
Pichia Anomala ◽  
Small Scale ◽  
Amylolytic Enzymes ◽  
Second Generation Bioethanol ◽  
Saccharification Efficiency ◽  
Ethanol Yields ◽  
Domestic Food

In the current study, a domestic food waste containing more than 50% of carbohydrates was assessed as feedstock to produce second-generation bioethanol. Aiming to the maximum exploitation of the carbohydrate fraction of the waste, its hydrolysis via cellulolytic and amylolytic enzymatic blends was investigated and the saccharification efficiency was assessed in each case. Fermentation experiments were performed using the non-conventional yeast Pichia anomala (Wickerhamomyces anomalus) under both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) modes to evaluate the conversion efficiencies and ethanol yields for different enzymatic loadings. It was shown that the fermentation efficiency of the yeast was not affected by the fermentation mode and was high for all handlings, reaching 83%, whereas the enzymatic blend containing the highest amount of both cellulolytic and amylolytic enzymes led to almost complete liquefaction of the waste, resulting also in ethanol yields reaching 141.06 ± 6.81 g ethanol/kg waste (0.40 ± 0.03 g ethanol/g consumed carbohydrates). In the sequel, a scale-up fermentation experiment was performed with the highest loading of enzymes in SHF mode, from which the maximum specific growth rate, μmax, and the biomass yield, Yx/s, of the yeast from the hydrolyzed waste were estimated. The ethanol yields that were achieved were similar to those of the respective small scale experiments reaching 138.67 ± 5.69 g ethanol/kg waste (0.40 ± 0.01 g ethanol/g consumed carbohydrates).

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