Enhanced human lysozyme production in biofilm reactor by Kluyveromyces lactis K7

Abstract

Lysozyme is an antimicrobial compound, which has been used in pharmaceutical and food industries. Chicken egg is the commercial source of lysozyme. However, human lysozyme is more effective and safer than egg-white lysozyme. Human milk is an important source for human lysozyme, but it is not feasible to provide the needed lysozyme commercially. Biofilm reactors provide passive immobilization of cells onto the solid support, which may lead to higher productivity. The aim was to evaluate the fermentation medium composition for enhanced human lysozyme production by Kluyveromyces lactis K7 in biofilm reactor with plastic composite supports. Yeast nitrogen base was selected as the best nitrogen source when compared to the yeast extract and corn steep liquor. Moreover, inhibition effect of NaCl and NH4Cl at the concentrations of 25 and 50mM was observed. Three factors Box–Behnken response surface design was conducted and the results suggested 16.3% lactose, 1.2% casamino acid, 0.8% yeast nitrogen base as optimum medium composition for maximum human lysozyme production. Overall, the human lysozyme production by K. lactis K7 was increased to 173U/ml, which is about 23% improvement in biofilm reactor and 57% improvement compared to the suspended-cell fermentation.