BIOCONVERSION OF CRUDE GLYCEROL INTO REUTERIN BY LACTOBACILLI ISOLATED FROM SILAGE

Abstract

Heterofermentative lactobacilli were isolated from sorghum and maize silage, and their ability to produce the antimicrobial compound reuterin (3-hydroxypropionaldehyde, 3-HPA) was investigated. Additionally, reuterin production from crude and partially purified biodiesel-derived glycerol was evaluated as an alternative to the utilization of these by-products. Only two out of 148 lactobacilli isolated produced reuterin in the presence of glycerol. The gene encoding a subunit of glycerol dehydratase was detected by PCR in isolates SO8 and SO23, identified as Lactobacillus reuteri by 16S rRNA gene sequence analysis. Levels of reuterin produced by these two isolates and strain L. reuteri DSM 17938, used as control, were different. For each bacteria, the amount of reuterin detected from biodiesel-derived glycerol was comparable with that obtained from aqueous solution of pure glycerol. Among silage isolates, L. reuteri SO23 yielded the highest levels of reuterin production. In addition, cell-free supernatants revealed inhibitory activity against silage spoilage microorganisms like spore-forming bacteria, yeast and mould. L. reuteri SO23 proved to be a valuable candidate for use of crude glycerol and its bioconversion to reuterin. Addition of glycerol together with reuterin-producing lactobacilli strains could represent a good alternative as silage biopreservant and help optimize profit in biodiesel production.