Recent advances in microbial transglutaminase biosynthesis and its application in the food industry

Microbial transglutaminase (MTGase) has been widely used to modify the functional properties of proteins in food systems. In the last 30 years since the discovery of MTGase, many efforts have been made on new strain isolation, culture media optimization, and fermentation procedure optimization to obtain MTGase with higher activity. Additionally, over the last decade, many studies have switched the focus from conventional optimization to genetic engineering in order to develop a highly efficient MTGase expression system with desired properties such as thermostability, activity, and yield by using genetic manipulation of strains such as Escherichia coli, Bacillus subtilis, and Pichia pastoris. In this review, we describe not only the recent advances and limitations related to MTGase biosynthesis but also the potential of MTGase for application in the food industry for some food products, including meat products, cheese, yogurt, and bread. Promoter engineering, gene codon optimization, signal peptide fusion, constitutive expression, random and rotational mutagenesis, etc. have been applied to enhance the recombinant expression system of MTGase. After three decades of research, the expression of recombinant MTGase has been significantly improved from the formation of inclusion body and enzyme with very low activity to the soluble form with high activity. Recombinant MTGase technology could also resolve problems related to post-translational modification in MTGase biosynthesis, resulting in facilitating downstream processing. In the future, it has been predicted that the scope of research will expand to work on heterologous expression by combination of genetic engineering tools. Further research is also needed to evaluate the biosynthesis of recombinant MTGase on a larger scale.