Abstract:

Enzyme is a kind of important ingredient of most liquid laundry detergent. Protease will autolyze and hydrolyze other enzymes in the liquid. By adding protease stabilizers, the activity of protease is inhibited temporarily, and the shelf life will be prolonged. There are already two commercialized stabilizers in the market, but they could not be used widely due to patent protection. Therefore, to develop other efficient stabilizers is very important for the users. The conventional verification test of stabilizers takes a very long time, so it is not suitable for high-throughput screening. Here this paper developed a simple and efficient screening method based on the principle that stabilizer is a reversible inhibitor. Firstly, the protease hydrolysis reaction of p-nitrophenyl acetate （p-NPA） was used to quantify the candidates’ inhibition ratio on protease, and then verified their stability efficiency in detergents. In addition, lipase can be used as an indicator to further shorten the experiment period. By this way, a variety of substances were evaluated and compared. As a result, 2, 6-difluoropyridine-3-boronic acid is found to be the most efficient one among the reported stabilizers, and 4-（alkylsulfonyl）phenylboronic acid may be also suitable as stabilizers. Finally, there is a positive moderate linear correlation between the protease inhibition ratio and the lipase residual rate in the protease-containing detergents, independent of protease species. The results indicate that this method is suitable for high-throughput screening of protease stabilizers and may be helpful for the development of detergent enzymes.

Key words: detergent enzymes, protease, stabilizer, inhibitor