Fermentative production of acetic acid from various pure and natural cellulosic materials by Clostridium lentocellum SG6

Clostridium lentocellum SG6 fermented various pure crystalline cellulosic m aterials efficiently with maximum acetic acid yield (gram acetic acid/gram substrate) of 0.67, at low substrate (8 g l(-1)) concentration. The strain grew poorly on crude biopolymers but fermented them easily after alkali tre atment, when grown with 8 g substrate l(-1) concentration of alkali-extract ed cotton straw (AECS), paddy straw (AEPS) and sorghum stover (AESS) etc. T he acetic acid to substrate (A/S) ratios were similar to those obtained wit h pure cellulosic materials. An increase in substrate concentration led to a decreased A/S ratio and a decreased percentage of substrate degraded. At high substrate concentration of 75 g filter paper l(-1), the strain SG6 con verted 63.2 g filter paper into 31.28 g acetic acid l(-1). At 100 g l(-1) c oncentrations, AECS and AEPS served as the best substrates for acetic acid production when compared with other biopolymers. A maximum amount of 30.98 and 30.86 g acetic acid was produced from 70.6 g AEPS and 70.1 g AESS l(-1) of medium by strain SG6, respectively. Acetic acid production of 0.67 g g( -1) pure cellulose (Whatman No. 1 filter paper), 0.63 g g(-1) of alkali-tre ated cotton straw (AECS) are the highest among the cellulolytic bacteria re ported so far in mono culture fermentations with pure and native cellulosic materials.