(544a) Effect of Inhibitory Compounds on Lactic Acid Fermentation By Lactobacillus Delbrueckii

Biomass pretreatments generate considerable inhibitors from the degradation of cellulose, hemicellulose, lignin and extractives, many of which inhibit the subsequent enzymatic hydrolysis and microbial fermentation. Identifying the potent inhibitors and developing selective chemical reactions to remove them are essential to convert lignocellulosic biomass to fuels and chemicals cost-effectively. In this study, the inhibitory effects of nine carbonyl model compounds (including furfural, 4-hydroxybenzaldehyde, syringaldehyde and 2, 3, 4-trihydroxybenzaldehyde) on lactic acid fermentation by Lactobacillus delbrueckii were investigated. It was observed that phenolic aldehyde compounds showed higher inhibition on cell growth and lactic acid productivity than furan aldehydes and benzoic acid. Particularly, 2, 3, 4-trihydroxybenzaldehyde was the most inhibitory compound on lactic acid fermentation. Quantitative structure-activity relationship (QSAR) modeling was used to build a correlation between biological toxicity of carbonyl compounds and their thiol reactivity.  A strong correlation between the carbonyl inhibition and electrophile reactivity was observed. Furthermore, we developed an environmentally friendly approach to detoxify 2, 3, 4-trihydroxybenzaldehyde and ortho-phthalaldehyde with H₂O₂ oxidation. The same strategy has been successfully used in the biomass hydrolysates detoxification for lactic acid fermentation.