Soluble recombinant transglutaminase for crosslinking plant protein hydrolysates

Cold-active transglutaminase (TGase) is highly valuable for their catalytic efficiency under low-temperature conditions, but not commercially available. This study investigated the recombinant expression of a cold-active TGase from Antarctic krill in Escherichia coli, achieving high solubility through induction optimization at 20 °C with 0.1 mM IPTG. The recombinant enzyme (rTGase) retained robust catalytic activity at 4 °C and effectively crosslinked pea protein hydrolysates (PPH), leading to improved molecular weight distribution and structural integrity. Analytical characterization via SDS-PAGE and MALDI-TOF revealed the formation of covalent isopeptide bonds, and spectroscopic and FTIR analyses demonstrated conformational rearrangement and increased molecular compactness in crosslinked PPH (CL-PPH). The rTGase-modified CL-PPH had improved thermal stability confirmed by thermogravimetric analysis. This study explored the production of a novel cold-active rTGase with demonstrated efficacy in tailoring the physicochemical properties of plant protein hydrolysates, providing a promising strategy for functional ingredient development in cold-processed food systems and other temperature-sensitive applications.