Encapsulation of Lactobacillus rhamnosus in Polyvinyl Alcohol for the production of L-(+)-Lactic Acid

Abstract

Poly(vinyl alcohol) (PVA) was investigated as a carrier for Lactobacillus rhamnosus ATCC 7469 cells for application in L-(+)-lactic acid (LA) fermentation on low-cost food industry by-products. Brewer's spent grain (BSG) and malt rootlets (MR) hydrolysates, with the addition of brewer's yeast, brewer's yeast extract, or malt rootlets extract and soy lecithin were evaluated as media for LA fermentation. PVA concentrations of 5, 10 and 15% were evaluated and the optimal concentration was further used. Obtained PVA biocatalyst (BC) was applied in batch and repeated batch fermentations of BSG and MR hydrolysate. During 12 consecutive batch fermentations, the BC showed high mechanical stability and minor loss of activity while achieving high LA yield (97%) and productivity (2.1 g/L h-1). The study suggests that the immobilized L. rhamnosus cells in PVA cryogel can be successfully used in stable repeated batch fermentations on low-cost fermentation media without the loss of cell activity and LA fermentation capability.