Improvement in Ethanol Yield from Lignocellulo-Starch Biomass using Saccharomyces cerevisiae Alone or its Co-culture with Scheffersomyces stipitis

Author(s): M.G. Mithra, G. Padmaja*.

Journal Name: Current Biotechnology

Volume 9 , Issue 1 , 2020

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Abstract:

Background: Literature on ethanol production from lignocellulo-starch biomass (LCSB) containing starch besides cellulose and hemicellulose, is scanty. Fed-batch separate hydrolysis and fermentation (F-SHF) was earlier found more beneficial than fed-batch simultaneous saccharification and fermentation (F-SSF).

Objective: The study aimed at modification of the saccharification and fermentation strategies by including a prehydrolysis step prior to the SSF and compared the ethanol yields with co-culture fermentation using hexose-fermenting Saccharomyces cerevisiae and pentose-fermenting Scheffersomyces stipitis.

Methods: Fed-batch hybrid-SSF and fed-batch separate hydrolysis and co-culture fermentation (F-SHCF) in improving ethanol yield from steam (ST) or dilute sulfuric acid (DSA) pretreated LCSBs (peels of root and vegetable crops) were studied.

Results: There was a progressive build-up of ethanol during F-HSSF up to 72 h and further production up to 120 h was negligible, with no difference among pretreatments. Despite very high ethanol production in the initial 24 h of fermentation by S.cerevisiae under F-SHCF, the further increase was negligible. A rapid hike in ethanol production was observed when S. stipitis was also supplemented because of xylose conversion to ethanol.

Conclusion: While ST gave higher ethanol (296-323 ml/kg) than DSA under F-HSSF, the latter was advantageous under F-SHCF for certain residues. Prehydrolysis (24 h; 50°C) enhanced initial sugar levels favouring fast fermentation and subsequent saccharification and fermentation occurred concurrently at 37°C for 120 h, thus leading to energy saving and hence F-HSSF was advantageous. Owing to the low hemicellulose content in LCSBs, the relative advantage of co-culture fermentation over monoculture fermentation was not significant.

Keywords: Lignocellulo-starch biomass, Ethanol, Fed-batch, Hybrid-SSF, Co-culture, F-SHF.

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Article Details

VOLUME: 9
ISSUE: 1
Year: 2020
Page: [60 - 79]
Pages: 20
DOI: 10.2174/2211550109666200311111119

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