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 72h and further production
up to 120h was negligible, with no difference among pretreatments. Despite very high ethanol
production in the initial 24h 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 (24h; 50°C) enhanced initial sugar
levels favouring fast fermentation and subsequent saccharification and fermentation occurred
concurrently at 37°C for 120h, 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.