Sustainable biobutanol production from Amorphophallus tuber starch via optimized ABE fermentation

Abstract

This study examines Amorphophallus tuber starch as a renewable carbon substrate for batch fermentation of acetone, butanol and ethanol (ABE) using Clostridium acetobutylicum TISTR. Scientists examined spent yeast extract as a potential economic substitute for conventional yeast extract as a nitrogen source. Batch fermentation of C. acetobutylicum required analysis of essential process parameters such as substrate concentration and nitrogen source selection and carbon source type, and pH values. The utilization of gelatinized Amorphophallus tuber starch by C. acetobutylicum led to a total solvent output of 28.45 g/L under uncontrolled pH conditions, which is similar to the 30.51 g/L solvent concentration attained with glucose. The highest solvent yield was observed during pure fermentation of gelatinized starch because enzymatic pretreatment failed to boost production, but acidic hydrolysis reduced solvent levels by 22.66%. Acidic conditions at pH 5.5 supported maximum solvent concentration (32.13 g/L), but pH 5.25 produced the highest acetone levels (6.59 g/L). The fermentation process at pH values above six promoted acidogenic pathways while producing minimal solvent amounts. Total solvent production reached its highest level of 28.56 g/L when the initial starch concentration was set at 70 g/L, yet lower concentrations under 30 g/L resulted in acidogenic metabolism. Recycled brewer's yeast extract produced solvents at a level that matched the performance of regular yeast extract by reaching 18.46 g/L. The findings from this research show that Amorphophallus tuber starch can effectively produce biobutanol with nutrients derived from brewery waste operations while supporting sustainable manufacturing approaches based on bio-circular economy sources.