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
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.