AUTHOR=Ma Tiange , Lu Jiaojiao , Zhu Jing , Li Xingjiang , Gu Hongwei , Montalbán-López Manuel , Wu Xuefeng , Luo Shuizhong , Zhao Yanyan , Jiang Shaotong , Zheng Zhi , Mu Dongdong 

TITLE=The Secretion of Streptomyces monbaraensis Transglutaminase From Lactococcus lactis and Immobilization on Porous Magnetic Nanoparticles

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01675

DOI=10.3389/fmicb.2019.01675

ISSN=1664-302X

ABSTRACT=<p>Microbial transglutaminase (MTG) from <italic>Streptomyces mobaraensis</italic> is an important enzyme widely applied in food processing for the improvement of protein properties by catalyzing the cross-linking of proteins. In this work we aimed at improving the production and enabling an easy and efficient purification process from culture supernatants. Thus, recombinant vectors, with either a constitutive promoter (P<italic><sub>p5</sub></italic>) or an inducible promoter (P<italic><sub>nisA</sub></italic>), controlling the expression of the MTG gene fused to the signal peptide of Usp45 (SP<italic><sub>usp45</sub></italic>) were constructed and then expressed in <italic>Lactococcus lactis</italic>. After purification, 43.5 ± 0.4 mg/L mature MTG-6His was obtained. It displayed 27.6 ± 0.5 U/mg enzymatic activity cross-linking soy protein isolate effectively. The purified mature MTG was immobilized with magnetic porous Fe<sub>3</sub>O<sub>4</sub> nanoparticles, which improved its activity up to 29.1 ± 0.4 U/mg. The immobilized MTG maintained 67.2% of the initial activity after being recycled for 10 times. The high production and secretion of functional <italic>S. mobaraensis</italic> MTG from <italic>L. lactis</italic> and the magnetic immobilized MTG-6His onto Fe<sub>3</sub>O<sub>4</sub> nanoparticles reported in this study would have potential industrial applications.</p>