Site-directed mutagenesis of NisinZ and properties of NisinZ mutants / 生物工程学报

According to the knowledge gained from engineering of nisinZ, using plasmid pHJ201 DNA as template, NisinZ was mutated by site-directed mutagenesis, NisinZ mutant T8S contains Serine at position 8 instead of Threonine, NisinZ mutant N27K/H31K contains Lysine at position 27 and 31, respectively, instead of Asparagine and Histidine and NisinZ mutant T2S/ H31K contains dehydrobutyrine and Lysine at position 2 and 31 instead of dehydroalanine and Histidine. They are cloned into pMG36e and expressed in L. Lactis NZ9800, the expression products of these mutants purified by Sephadex CM-25 and Sephadex G-25 chromatography, some properties of NisinZ mutants (T8S, T2S/H31K and N27K/H31K) were studied. The results showed that the spectrum of antimicrobial activity and solubility of these mutants had not been changed, their antimicrobial activities were found to be slightly lower than that of the wild-type NisinZ. but mutants T8S and T2S/H31K showed higher stability, which were significantly more stable than wild-type NisinZ at 55 approximately 100 degrees C and pH7 approximately 9.

Food-grade gene expression systems for lactic acid bacteria / 生物工程学报

Lactic acid bacteria (LAB) are important industrial microorganism used in the production and preservation of food-stuffs. Recently, considerable advances have been made in the genetics and molecular biology of LAB. These have resulted in the construction of food-grade gene expression systems for these bacteria. This paper aims to review the essential features for food-grade systems, food-grade selection markers, food-grade controlled gene expression and food-grade inducible signaling molecule, and recent developments on food-grade cloning and expression systems for LAB. These gene expression systems have great potential for studies on gene expression and regulation in LAB and a variety of bioprocessing application in industrial fermentations.