Utilization and production of single activity enzymes from Aspergillus nidulans

Abstract

Scope and Method of Study: The first objective was to determine the synergistic effects of enzyme mixtures for maximum enzymatic hydrolysis of grain sorghum stover untreated and pretreated with liquid hot water pretreatment. The second objective was to determine the feasibility of continuous client enzyme production with an Aspergillus nidulans mutant containing a pyridoxine marker by limiting the supply of pyridoxine. The third objective was to determine the feasibility of using the limited growth system with pyridoxine limitation in a trickle bed reactor for prolonged client enzyme production.

Findings and Conclusions: The usage of accessory enzymes together with the commercial available cellulolytic enzyme Cellic CTec2 from Novozymes did not improve the enzymatic hydrolysis of grain sorghum stover. The best glucose and xylose conversion observed was 77% and 68% respectively, achieved on pretreated grain sorghum stover with CTec2.

Pyridoxine limitation was successfully shown to have no effect on XynB production compared to a culture grown with pyridoxine. Additionally, it was observed that the culture did not grow when pyridoxine was absent. A successful demonstration of continuous XynB production with the trickle bed reactor was shown over a period of 18 days. The reactor achieved a XynB output of 41 U/ml with an influent and effluent flow rate of 0.5 ml/min and a recycle flow rate of 56 ml/min. Production yields are higher compared to a static tray culture and SSF enzyme production stated in the literature.