Abstract
Study of production of lactic acid from newspaper hydrolysate in shake flasks by a bacterial strain; SU-1 isolated from silage was carried out. Parameters such as hydrolysate concentration, pH and shaking speed were examined. Lactic acid product yields (at 37 °C, pH 7 and 150 rpm) of 0.42 and 0.33 were obtained when MRS medium containing 60 and 80 % (v/v) (total sugar amounts of 15 and 20 g/l) hydrolysate, respectively, were used. While using 40% (v/v) (equivalent to 10 g total sugar/l) hydrolysate as carbon source, the bacterial strain; SU-1 produced lactic acid in small amount (Yp/s = 0.03). The bacterial growth was very low when cultured in 100 % hydrolysate (29 g total sugar/l). Study of the effect of pH on lactic acid production from the hydrolysate showed that the bacterial strain; SU-1 preferred the medium with pH 7 than pH 5 (Yp/s = 0.42 and 0.38, respectively). Increase in the shaking speed from 50 to 100 and 150 rpm improved the lactic acid yields from 0.13 to 0.22 and 0.42, respectively, but when the shaking speed reached 200 rpm the lactic acid yield decreased to 0.25. 16S Ribosomal DNA sequence analysis of SU-1 showed 95 (13–605 bp) and 98% (936–1401 bp) similarity of nucleotide sequences to Enterococcus faecium.
Keywords
Lactic acid; Cellulose; Hydrolysate; Newspaper
