Abstract:

To enhance the utilization rate of straw， two cellulose-degrading bacteria were isolated from the intestinal tract of termites. The bacteria were initially screened using Congo red and subsequently re-screened with a filter paper degradation test. They were identified as Cellulomonas iranensis （CE） and Bacillus safensis （BS） through NCBI homologous sequence alignment. The enzymatic activities of endoglucanase， exoglucanase， and β-glucosidase were quantified to two bacterial species. The measured activities for BS were 0.102， 0.321， and 0.112 U·mL^-1， respectively， whereas those for CE were 0.202， 0.434， and 0.131 U·mL^-1， respectively. The differential metabolites identified during filter paper fermentation by BS and CE were primarily amino acids and their metabolites， benzene and its derivatives， aldehydes， ketones， esters， alkaloids， organic acids and their derivatives， as well as heterocyclic compounds. The differential metabolic pathways were dominated by the biosynthesis of phenylalanine， tyrosine， and tryptophan， as well as the degradation of aromatic compounds. After 14 days fermentation， BS and CE were cultivated with rice （Oryza sativa） straw as the sole carbon source. The straw was degraded to varying degrees. Both of BS and CE significantly （P<0.05） reduced the contents of acid detergent fiber （48.80%， 35.43% DM）， hemicellulose （19.90%， 17.53% DM） and water soluble carbohydrate （0.11%， 0.18% DM）. In addition， the inoculation of CE also obviously increased （P<0.05） the weight loss rate of straw （43.12% DM） and reduced the content of neutral detergent fiber （52.95% DM）.

Key words: cellulose-degrading bacteria, filter paper, rice straw