Study On The Biological Characteristics Of A Cellulolytic Bacteria Strain

A newly isolated strain of the bacterium DS-0501 which can grow on cellulosic filter paper has the rapid growing velocity .It can degrade cellulose effectively .The morphological and physiological properties of this strain were studied.According to part of the 16SrDNA sequences analysis,the strain was identified as a new strain of DS-0501.The new strain of cellulolytic bacteria was isolated from soil by filter paper plate,the result showed that this strain have a strong ability to decompose the filter paper cellulose.the yellow colonies appeared when this strain is inoculated for 3 days on cellulosic filter paper plate in 31℃.After 6 days, cellulosic filter paper was totally degraded.The strain sp. DS-0501 was cultured in 5 different liquid state culture mediums for four days. CMCase, FPase activity in each medium and the degradation time of cultivation were compared so that the optimal fermentation medium state is decided.that was : Mandel salt +1% filter paper.In the base of the original fermentation medium, the optimum culture conditions was studied. The culture conditions included initial pH of medium, inoculation amount, velocity of shaker and temperature.The results showed that the optimum conditions of producing cellulase are as follows:The temperature is 30℃-32℃, the initial pH is 7.0, the shaking speed is 140r/min, meanwhile 5% inoculation amount facilitates cellulase production. The highest cellulase activities are obtained by using 1% cellulosic filter paper and Mandel salt.The crude cellulase from liquid medium were studied .The result showed that CMC activity were 25.68U,8.44U and 7.54U in the supernatant , liquid of cell broken and cell suspension in respectively.Further showed that the CMCase was extracellular enzyme and most FPAase existed in cells, small part of the FPAase was out of cells.The crude cellulase was purified by ammonium sulfate fractionation, dialysis and freeze-drying. The anlysis shows that the optimum temperature of CMCase activity was 50℃, while the optimum temperature of FPAase activity was 40℃. Both The optimal crude cellulase activity was studied in the pH range of 4.0-5.0.The optimum pH of both CMCase and FPAase was 5.0. When the temperature was 40℃-50℃and the pH was 4.0-5.0, both CMCase and FPAase were stabilified.Because the capsule, which were producted by stain DS0501,was mucilaginous, the powders of crude enzyme included more polysaccharides. It bringed some question for the purification, so some new purification methods should be adopted for the purification.