Two-stage fermentation for lactic acid production on distillery stillage

Abstract

The aim of this study was to assess utilization of distillery stillage in a two-stage fermentation using Bacillus licheniformis TFUNS and Lactobacillus paracasei NRRL B-4564. In the first stage the stillage was pretreated with B. licheniformis which is an efficient producer of proteolytic enzymes, in order to increase the content of free α-amino nitrogen in the waste substrate. In the subsequent stage the lactic acid (LA) fermentation by L. paracasei was performed. The results of the fermentation of proteolytically pretreated stillage (i.e. of two-stage fermentation) were compared with the untreated stillage (one-stage fermentation). The results have shown that the amount of free α-amino nitrogen in pretreated media was 107 % higher compared to the initial value. The concentration of the LA obtained in the second stage by L. paracasei was 48 % higher than in untreated stillage. In addition, the growth of L. paracasei in pretreated stillage was also better supported compared to that in untreated media. The process enabled economical and sufficient supply of easily assimilative nitrogen sources needed for lactic acid bacteria, thus avoiding addition of costly sources in the media commonly performed in LA production.