Dissolved oxygen on xylanase production by Trichoderma reesei using Reutalis trisperma press cake as an additional substrate

Abstract

Dissolved oxygen (DO) level in media plays a big role in the succession of the fermentation process by a microorganism. In this project, Trichoderma reesei was cultivated in two types of media, media A and B, both in 250 mL shake flask and 1.5 L fermenter at varying DO level. Media A and B contained the same carbon source and mineral salts, the difference between both media was the presence of press cake in Media B as urea and ammonium sulfate replacement, whereas the nitrogen sources in media A consists of urea and ammonium sulfate. The batch fermentation process was conducted in a 7.8 C/N ratio with an initial pH of 6. The purified enzyme was shown to convert xylan to xylose. Media B that contained Reutealis trisperma press cake gives a higher xylanase activity than media A without press cake, for both shake flask and fermenter cultivations. A xylanase activity of 101.07±1.65 U/mL and 39.30±0.64 U/mL was produced in a shake flask under 140 rpm for 96 hours of fermentation with ratio of 0.6 media B/flask volume and 0.6 media A/flask volume, respectively. A xylanase activity of 205.90±0.84 U/mL and 88.87±1.45 U/mL was produced in 72 hours at 0.8 L/min of aeration rate in a 1.5 L fermenter with media A and media B, respectively. Thus, this study identified the Reutealis trisperma cake can be used as a beneficial additional substrate and nitrogen sources. The increase in DO level, which indicated by increasing aeration rate, can generate a higher xylanase activity for both media in shake flask and fermenter.