Construction Of Engineering Strain With High Production Of TGase And Study On Optimization And Application Of Modified SPI Films

Edible films have received great interest in food preservation and been used widely. Interest and research activity in soy protein isolate (SPI) film have been especially intense all around the world. The subject to Bacillus subtilis gene as template, obtained by genetic engineering technology for the modification of edible SPI film transglutaminase (TGase), and optimize the films preparation process, on the basis of the modified SPI films used in the feasibility of preserved nuts and fruits. The main contents and results were as follows:(1)Experiment with genomic DNA of Bacillus subtilis as template, according to TGase gene sequence, synthesis of primers, transglutaminase gene (tg) was amplified by PCR, and inserted into the vector pGM-T in the digestion and sequencing to identify the correct recombinant plasmids were digested, ligation, constructed expression plasmid pET-tg, The recombinant plasmid was then transformed into E.coli BL21(DE3), induce and expression the recombinant, determining the optimal induction time was 5 h, optimum induction temperature was 25℃.(2) Use of obtained TGase modified SPI films, and the films performance as an index determined by single-factor test SPI concentration, glycerol concentration, enzyme concentration, pH, drying temperature on the properties of SPI films. The impact of various factors to determine the optimal range, while the membrane properties of selected significant factors compared for the secondary orthogonal rotation optimization test, analysis the test data by a statistical analysis software of SAS8.2, obtaind the optimal modification SPI films-forming conditions: drying by room temperature, SPI concentration was 5.12%, glycerol concentration was 2.04%, TGase concentration was 0.21%, pH was 8.40.(3) Nuts and fruits were coated with modified SPI membrane liquid,walnuts and almonds stored at 60℃for 10 days, the peroxide value decreased by 49% and 36%, acid value decreased for 42% and 40% compared to uncoated samples. Cherry tomatoes coated with modified SPI membrane, it can inhibit the cherry tomatoes metabolism, reduce the loss of nutrients, reducing the decay rate, weight loss, and acid content, inhibition of their respiration.