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Bioconversion of green volatiles in okara (soybean residue) into esters by coupling enzyme catalysis and yeast (Lindnera saturnus) fermentation

Vong, Weng Chan, Liu, Shao-Quan
Applied microbiology and biotechnology 2018 v.102 no.23 pp. 10017-10026
tofu, Cyberlindnera saturnus, fermentation, linoleate 13S-lipoxygenase, soybeans, yeasts, byproducts, carboxylic ester hydrolases, esters, biotransformation, soymilk, catalytic activity, aldehydes, off odors
Okara (soybean residue), a by-product from soymilk and tofu production, has a green, grassy off odour as it contains a large amount of aldehydes. This work investigated the rate-limiting enzyme(s) in the formation of aldehydes in okara and the pathways leading to their bioconversion into fruity, pleasant-smelling esters by the yeast Lindnera saturnus. Lipase and hydroperoxide lyase were shown to be rate-limiting enzymes while endogenous soy lipoxygenase was also crucial for the production of aldehydes in okara. Subsequent fermentation of okara by L. saturnus increased the amount of esters by about 70 times to 165–277 μg/g dried okara. The generation of C7 esters followed our hypothesised pathway, while that for C6 esters was mainly affected by L. saturnus. This study presents a simple and inexpensive one-pot setup for the natural bio-production of esters from okara.