Bioconversion of photooxidatively delignified woody biomass of Salix alba into bioethanol using C6/C5 co- sugar fermenting yeast Pichia kudriavzevii BGY1
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Date
2021-03
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Presently bioethanol is considered as the most sustainable and eco- friendly fuel in contrast to non- renewable fuels. The present study was carried out for identification and characterization of potential ethanogenic yeast. Native yeast cultures were isolated from diverse fruit sources. Based on qualitative and quantitative screening for ethanol production two ethanogenic yeast were selected and subjected to UV and gamma mutagenesis with aim to enhance stress tolerance limit and sugar fermenting ability. Based on phenotypic and 5.8 S ITS rRNA gene sequencing, the isolate BGY1 and its mutant BGY1- γ m were identified as Pichia kudriavzevii BGY1 and Pichia kudriavzevii BGY1- γ m. The woody biomass of Salix alba was first subjected to chemical, biological, chemi- biological and photonanocatalyst mediated pretreatments for removing lignin and improving saccharification efficiency. Combined photonanocatalyst induced and cellulase enzyme aided alkaline oxidative pretreatment decreased the lignin content from 18.7 to 4.0 %. The pretreated substrate was then saccharified into fermentable sugars using cellulase enzyme from the fungal isolate (Aspergillus terrus PPCF). Optimization of saccharification resulted in 57.2 % of saccharification efficiency in 24 h. Then, the potential microbial strains in mono/co-cultures were screened for their alcohol producing efficacies using saccharified Salix alba wood biomass. Bio-conversion of saccharified wood employing potential strains into bio-ethanol was carried out in batch cultures through SHF and SSF process. Finally the co- culture of P. Kudriavzevii BGY1 and P. Kudriavzevii BGY1-γ m were selected for alcoholic fermentation. Alcoholic fermentation of saccharified Salix alba wood powder using co- culture of yeast P. kudriavzevii BGY1 and P. kudriavzevii BGY1- γ m at 32º C under SSF batch fermentation process was found superior over batch fermentation under SHF process. Under optimized conditions maximum ethanol yield 13.0 % was achieved with saccharified Salix alba wood.