Mutation breeding of lipase-producing strain Flavobacterium sp. by supercritical CO2 with hydrazine hydrate

This work aimed to obtain an ideal mutant strain with higher lipase yield using hydrazine hydrate (HZH) as a novel additive to treat Flavobacterium sp. strain YY25 by supercritical CO2. The survival rate and the positive mutation rate of the tested strain were strongly dependent on the dose of HZH. The treatment by 0.5% HZH in supercritical CO2 (8 MPa, 35°C) for 30 min provided 58.3% of positive mutation rate and an expected mutant strain with about 76.7% increase in lipase yield compared with the wild strain. Possible mutagenesis mechanisms were further explored. The analysis on pH drop of the treated seed liquid was performed to better understand the interaction. Results proved that the induced mutation with enhanced yield of lipase could be achieved by co-mutagenesis of supercritical CO2 and HZH.

Use of chitosan gel for the purification of protein

The aim of this study was to optimize the preparation of chitosan gel and to use it for protein purification. The optimized preparation parameters were chitosan concentration 2.0 percent, glutaraldehyde concentration 0.6 percent, low cross-linking rate, NaOH concentration 1.6 percent, amount of NaBH4 0.4 g. In order to use the chitosan gel, the elution conditions were optimized as follows. NaCl concentration 0.05 mol/L in the tris-HCl (pH 9.05) at the flow rate of 2.03.0 mL/min. Particle size of chitosan gel was 120-140 µm. Neutral protease could be separated into four ingredients through chitosan gel column. The yield of enzyme was more than 90 percent. Albumin bovine serum could be separated into two ingredients through gel column and the total yield of albumin bovine serum was more than 70 percent.