Effect And Control Of Dissolved Oxygen On The Cellulase Production By Trechoderma Reesei

The effect and control of dissolved oxygen in the cellulase production by Trechoderma reesei were studied with pulp of 10g/l.. The experiments were first carried in the 10L steam sterilizable bioreactor and with aeration rate of 25L/(h.l). By not controlling pH or controlling pH of 4.8, the variety of H+ concentration in the growth of mycelium and effect of H+ concentration on the growth and production were studied; By adding to aeration rate of 30L/(h·l), effect of aeration on the growth and production were studied; by controlling DOT40%-50%, 30%-40% and 20%-30% respectively, effect of dissolved oxygen tension on mycelium growth and cellulase production were studied. Then the experiments were carried in the 2L steam sterilizable bioreactor. By control aeration rate of 25L/(h·l) or DOT 20%-30%, measuring oxygen and carbon dioxide content, the variety of oxygen and carbon dioxide in the mycelium growth were studied, the results were showed:H+ concentration was fluctuated in the growth and metabolize of Trechoderma reesei. Glucose in the culture medium was utilized to produce acidity substance, so H+ concentration would gradually rise. Synchronously, it would bring on decline of H+ concentration that portion of mycelium autolyzed, turn out increased of H+ concentration in culture, which went against growth of mycelium and cellulase production. Activity ofβ- glucosidases in the cellulase was low and its harvest was low when it hydrolyzed. The yield of enzymatic hydrolysis was 55.7% at 48h and was 56.7% at 72h,cellobiose content was 0.943g/l that was high. It was in favor of growth and metalize of mycelium that control culture to pH4.8, and it increased ability of cellulase production. The most of mycelium mass concentration was increased from 2.60g/l to 2.77g/l, increased 6.5%. the most of filter paper activity was raised from 1.87IU/ml to 2.79iu/ml ,increased 0.92IU/ml, enhanced 49.2%.Trechoderma reesei needs more dissolved oxygen in the growth and metabolize. Increasing aeration can increase dissolved oxygen, which is in favor of mycelium growth, and enhance ability of cellulase production. When aeration was increased to 30L/(h.l) , level of dissolved oxygen was enhanced and mass concentration of mycelium was increased from 2.77g/l to 2.98g/l, by 7.6%, filter paper activity was raised from 2.79Iu/ml to 2.98IU/ml, by 6.8%.Controlling pH and increasing aeration enhanced the activity of cellulase and yield of cellulase as well as the velocity of reaction, so that so that the cellulase was more high-yielded. When controlling pH4.8, the productivity of cellulose at the maximum of paper activity was increasing from 22.18IU/(h.l) to 33.26IU/(h.l), by 50.0%; while as the aeration was added to 30L/(h.l), the productivity was increasing from 33.26IU/(h.l) to 38.21IU/(h.l), by 14.9%.Controlling DOT20%-30% makes the optimum dissolved oxygen for the growth and metabolism of mycelium. When DOT was controlled to 40 %-50%, 30%-40% and 20%-30%, the growth of mycelium was quickening in turn, and the highest mass concentrations of mycelium were 3.01g/l, 6.06g/l and 3.12g/l respectively. The velocity of utilizing glucose quickened, then the cellulose could induce the synthesis of cellulase earlier. The filter paper activity at 24h were respectively 0.12IU/ml, 0.37Iu/ml and 0.63Iu/ml. At 92h, 80h and 76h, the filter paper activity were the highest.Controlling DOT 20%-30% accelerated the synthesis of cellulase by Trechoderma reesei. When controlled DOT 40%-50%, 30%-40% and 20%-30%, respectively, the most of filter paper activity were 3.09IU/ml,3.26IU/ml and 3.55IU/ml. The cellulase's total output was more than that of fixing the aeration at 30L/(h.l), with the rate of enhancement at 3.7%, 9.4% and 19.1%. The cellulase's throughput of each mass mycelium was enhanced by 2.7%,6.5% and 13.8% respectively.When controlled DOT 20%-30%, there was a more rational structure in enzyme system with a higher filter paper activity as well as a higher yield of enzymatic hydrolysis, and cellobiose in the hydrolyzing liquid was lower. The yield of enzymatic hydrolysis at 48h was 59.26% and the cellobiose content was 0.233g/l; the yield of enzymatic hydrolysis was 63.43% and cellobiose was 0.199g/l at 72h.When DOT was controlled to 20%-30%, the aeration of mycelium at the main period of growth and metabolism increased, with a higher Moore content in oxygen. Higher oxygen content in gas was propitious to the dissolution of oxygen and the acceleration of its transmission, so that the oxygen uptake rate OUR was enhanced in the fast growth phase of mycelium and the rising trend of OUR was consistent with the change of the quantity of mycelium's growth. The thickest mass concentration of mycelium increased to 3.11g/l, 11.8% thicker than that of fixing the aeration rate at 25L/(h.l) while the mass concentration was 2.78g/l. The oxygen uptake of mycelium was stable, and it was in favor of the stability of cell plasmid and the expression of gene.When controlled DOT 20%-30%, the Moore content of the carbon dioxide in the gas occupied 0.4%,half of 0.8% when fixed the aeration at 25 L/(h.l). Dissolved carbon dioxide in the culture could be released into the gas quickly and therefore discharged. The rate of releasing of carbon dioxide CER was also higher. The mycelium was growing and metabolizing stably. The period of 0-20h was its main growth phase, when RQ was about 0.6; 20-60h, phase of growing and metabolizing, when RQ was about 0.8; after 60h comes its main phase of metabolism, when RQ was about 1.When controlled DOT 20%-30%, the productivity of cellulase was 354IU/g, 28.8% higher than 275IU/g of the aeration rate at 25L/(h.l), i.e overall throughput of cellulase was enhanced by 28.7%. The mass concentration of mycelium was increased by 11.8%, while the cellulase throughput of each mass mycelium was enhanced by 15.1%; both made overall throughput of cellulase enhanced by 28.7%. Synchronously, the productivity of cellulase was enhanced by 50.2% for the faster growth of mycelium.The filter paper activity of cellulase increased to 2.79IU/ml by controlling pH4.8, and was 49.2% higher than 1.87IU/ml when not controlling pH. By controlling pH4.8 and DOT20%-30%, filter paper activity of cellulase increased more to 3.54IU/ml, by 26.9%. The total proportion of the two steps was 89.3%, namely, the productivity of cellulase was enhanced by 89.3%. Moreover, the period of reaction was shortened from 84h to 72h, while the overall production efficiency of cellulase was enhanced by 120.9%. In conclusion, by controlling pH and DOT, the productivity of cellulase was enhanced by 89.3%; the efficiency of cellulase production was enhanced by 120.9%.