(465b) Glucose/Pachymaran Co-Feeding Enhanced Endo-?-1,3-Glucanase Production By Trichoderma Harzianum Via Improving Cell Concentration and Maintaining Induction Effects

We have previously demonstrated that endo-beta-1,3-glucanase from Trichoderma
harzianum could be used to effectively hydrolyze curdlan in a wide range of
oligosaccharide productions. Due to the induction effects of pachymaran as
polysaccharide, production of endo-beta-1,3-glucanase with
pachymaran as a sole carbon source reached 86.1 U/mL, 2.2-fold higher than that
of control, in which glucose was a sole carbon source. However, the cell
concentration decreased from 25 to 12 g/L during the late stage of fermentation
due to cell degradation by endo-beta-1,3-glucanase. Glucose/pachymaran
co-feeding strategy was thus carried out in a 7-L fermenter to ensure high cell
concentration and endo-beta-1,3-glucanase production. Firstly,
glucose concentration was optimized and set at 30% in the mixed carbon sources
by comparing the fermentation performances under varied carbon proportions.
Secondly, a novel fed-bacth feeding strategy was applied: glucose was fed twice
during logarithmic growth phase (24 and 48 h), and subsequently, pachymaran was
fed once during initial stage of the target enzyme accumulation phase (72 h).
With this multi-stage feeding strategy, the production of endo-beta-1,3-glucanase
reached 721.5 U/mL, 26-fold higher than that of control. In addition, the cell
concentration remained to stay as high as 30 g/L throughout the course of
fermentation. Finally, various
factors affecting stability and activity of endo-beta-1,3-glucanase were analyzed. The optimal hydrolysis
conditions were found to be: time = 2.5 h, pH = 5.5, and temperature 50 ^oC.
While endo-beta-1,3-glucanase activity could be inhibited by Ag⁺,
Hg²⁺, K⁺, Al³⁺, and Fe³⁺, as a
certain concentration, Mg²⁺, Mn²⁺, Cu²⁺ and Zn²⁺
could activate such activity.