High-yield recombinant xylanase production by Aspergillus nidulans under pyridoxine limitation.

The present study investigated the limitation of pyridoxine on an Aspergillus nidulans culture that produces xylanase B (XynB) as a client enzyme and was unable to synthesize pyridoxine. This technique was used to limit cell growth and divert substrate to product formation for a surface grown culture that could be used in trickle bed reactors. It was observed that growth was limited when pyridoxine was absent, while enzyme production was unaffected. Enzyme production was 1,026 U after 480 h of continuous fermentation, which was similar to a culture that grew on medium with pyridoxine. Furthermore, the present study investigated the growth rate of A. nidulans with pyridoxine in the medium and determined the productivity of XynB production with and without pyridoxine. A maximum growth rate of 0.311/h was observed. The maximum XynB productivity of 21.14 U/g h was achieved when pyridoxine was not added to the medium.