Optimization of Process Parameters for ε

ε-Polylysine (ε-PL) is a highly safe natural food preservative with a broad antimicrobial spectrum, excellent corrosion resistances, and great commercial potentials. In the present work, we evaluated the ε-PL adsorption performances of HZB-3B and D155 resins and optimized the adsorption and desorption conditions by single-factor test, response surface method, and orthogonal design. The complexes of resin and ε-PL were characterized by SEM and FITR. The results indicated that D155 resin had the best ε-PL adsorption performance and was selected for the separation and purification of ε-PL. The conditions for the static adsorption of ε-PL on D155 resin were optimized as follows: ε-PL solution 40 g/L, pH 8.5, resins 15 g/L, and absorption time 14 h. The adsorption efficiency of ε-PL under the optimal conditions was 96.84%. The ε-PL adsorbed on the D155 resin was easily desorbed with 0.4 mol/L HCl at 30°C in 10 h. The highest desorption efficiency was 97.57% and the overall recovery of ε-PL was 94.49% under the optimal conditions. The excellent ε-PL adsorption and desorption properties of D155 resin including high selectivity and adsorption capacity, easy desorption, and high stability make it a good candidate for the isolation of ε-PL from fermentation broths

Lignin-induced Expression of Aspergillus oryzae 5992 Genes using Suppression Subtractive Hybridization

A previous study reported that a novel Aspergillus oryzae strain (CGMCC5992) can synthesize lignin hydrolytic enzymes for lignin degradation from straw. The present work involves the different gene expression of A. oryzae 5992 grown in media using lignin and glucose as carbon sources by suppression subtractive hybridization. Surprisingly, peroxidase was found in up-regulation genes, which is the key enzyme for degrading lignin. This shows that A. oryzae 5992 can secrete peroxidase in the presence of lignin. The functions of up-regulation genes also included gluconeogenesis, repairs, as well as signal and transporter proteins in the cell membrane. In addition, the down-regulation of genes was closely related to the aerobic metabolism of glucose, the fatty acid synthesis of the cell membrane, and the synthesis and utilization of ATP. Therefore, A. oryzae could regulate metabolism using lignin as carbon source, including lignin degradation promotion, glucose metabolism inhibition, and glucose regeneration