Crude glycerol from biodiesel as a carbon source for production of a recombinant highly thermostable β-mannanase by Pichia pastoris.

Abstract

To explore an efficient use of crude glycerol for the production of a highly thermostable β-mannanase (ReTMan26) by Pichia pastoris X33. Cell growth was significantly inhibited by 4 and 6% (w/v) crude glycerol in 250ml shake-flasks and in 5l bioreactor batch cultures, respectively, but not affected by pure glycerol at the same concentrations. For further study, the impact of various impurities in crude glycerol on the cell growth of, and ReTMan26 production by, Pichia pastoris was investigated. Salts and methanol did not exert an inhibitory effect, but ≥0.2% and 0.3% (w/v) soap in shake-flask and bioreactor cultures, respectively, inhibited fermentation. Under identical conditions, the biomass and ReTMan26 activity produced by high-cell-density fermentation using 5% crude glycerol (glycerol at 80%, w/w) were slightly higher than those using 4% (w/v) pure glycerol. Non-pretreated≤5% (w/v) crude glycerol could be effectively utilized for industrial production of ReTMan26, and the total production costs using crude glycerol were ~4.2% lower than those using pure glycerol.