Identification and characterization of Clostridium paraputrificum, a chitinolytic bacterium of human digestive tract

Abstract

A strictly anaerobic, mesophilic and chitinolytic bacterial strain was isolated from human feces. Based on morphological and physiological properties and 16S rRNA sequence analysis the strain was identified as Clostridium paraputrificum. The strain utilized chitin and N-acetyl-D-glucosamine, grew on glucose and hydrolyzed starch. Cultivation of the strain with colloidal chitin as the growth substrate resulted in the production of gas (hydrogen and carbon dioxide) and formation of acetate and lactate (21.6 and 18.9 mmol/L, respectively) and only small quantities of propionate and butyrate (1.7 and 2.6 mmol/L, respectively). In the course of a 10-d cultivation with chitin, the endochitinase activity was detected after 1 d and gradually increased, reaching maximum after 3 d (251 nkat/L N-acetyl-D-glucosamine). The beta-N-acetylglucosaminidase activity appeared just at the beginning of the cultivation, increased to day 2 and then remained nearly constant. More than 90% of chitin added was degraded within 2 d of cultivation. On the zymogram of the extracellular chitinolytic complex were visible at least 6 isoenzymes with molar mass 43.5-65.0 kDa. The temperature optimum of endochitinase and beta-N-acetylglucosaminidase activities was 50 degrees C; the optimum activity of both enzymes was found at pH 4-6.