Simultaneous saccharification and ethanologenic fermentation (SSF) of waste bread by an amylolytic Parageobacillus thermoglucosidasius strain TM333

The starch in waste bread (WB) from industrial sandwich production was directly converted to ethanol by an amylolytic, ethanologenic thermophile (Parageobacillus thermoglucosidasius strain TM333) under 5 different simultaneous saccharification and fermentation (SSF) regimes. Crude alpha-amylase from TM333 was used alone or in the presence of amyloglucosidase (AMG), a starch monomerizing enzyme used in industry, with/without prior gelatinisation/liquefaction treatments and P. thermoglucosidasius TM333 fermentation compared with Saccharomyces cerevisiae as a control. Results suggest that TM333 can ferment WB using SSF with yields of 94-100% of theoretical (based on all sugars in WB) in 48 h without the need for AMG addition or any form of heat pre-treatment. This indicates that TM333 can transport and ferment all of the malto-oligosaccharides generated by its alpha-amylase. In the yeast control experiments, addition of AMG together with the crude alpha-amylase was necessary for full fermentation over the same time period. This suggests that industrial fermentation of WB starch to bio-ethanol or other products using an enhanced amylolytic P. thermoglucosidasius strain could offer significant cost savings compared to alternatives requiring enzyme supplementation.

Automated summary

This study demonstrates the potential of using a thermophilic bacteria strain, Parageobacillus thermoglucosidasius, for direct conversion of waste bread starch into ethanol. The strain achieved high ethanol yields without the need for additional enzymes or heat treatment, making it a cost-effective alternative for industrial bio-ethanol production.