Abstract
Enzymes are considered an innovative and environmentally friendly approach for biofilm control due to their lytic and dispersal activities. In this study, four enzymes (beta-glucanase, alpha-amylase, lipase and protease) were tested separately and in combination with the quaternary ammonium compound cetyltrimethylammonium bromide (CTAB) to control flow-generated biofilms of Pseudomonas fluorescens. The four enzymes caused modest reduction of biofilm colony forming units (CFU). Protease, beta-glucanase and alpha-amylase also caused modest biofilm removal. CTAB combined with either beta-glucanase or alpha-amylase increased biofilm removal. Its combination with either beta-glucanase or protease increased CFU reduction. However, CTAB - protease combination was antagonist in biofilm removal. Long-term effects in biofilm mass reduction were observed after protease exposure. In contrast, biofilms treated with beta-glucanase were able to regrow significantly after exposure. Moreover, short-term respirometry tests with planktonic cells were performed to understand the effects of enzymes and their combination with CTAB on P. fluorescens viability. Protease and lipase demonstrated antimicrobial action, while alpha-amylase increased bacterial metabolic activity. The combination of CTAB with either protease or alpha-amylase was antagonistic, decreasing the antimicrobial action of CTAB. The overall results demonstrate a modest effect of the selected enzymes in biofilm control, either when applied alone or each one in combination with CTAB. Total biofilm removal or CFU reduction was not achieved and, in some cases, the use of enzymes antagonized the effects of CTAB. The results also propose that complementary tests, to characterize biofilm integrity and microbial viability, are required when someone is trying to assess the role of novel biocide - enzyme mixtures for effective biofilm control. (C) 2017 Published by Elsevier Ltd.