Screening of Marine Bacteria for Lipase Activity and Application as Whole-Cell Biocatalysts.

Several strategies can be employed for the identification of novel microbial lipases. Despite the increasing importance of metagenomics in bioprospecting, significant limitations in the expression of recombinant proteins, and lipases in particular, remain. Culture-based bioprospecting approaches are, therefore, still valuable. In this work, a collection of bacterial isolates, mainly of marine origin, was screened for lipase activity through a culture-based approach. Screening for lipolytic bacteria was performed in solid media containing olive oil emulsions and rhodamine B. Positive isolates were subsequently grown in liquid media, to confirm lipase production. Significant hydrolytic activity towards the triglyceride substrates tributyrin and triolein could be observed with the biomass produced, although no lipase activity could be detected in the culture supernatants. Six isolates presenting high activity were characterized as whole-cell biocatalysts, and all were found to be active at temperatures ranging between 25 and 65 °C, and at pH values between 6 and 10.5. Genomic analyses of two of these Gram-negative lipase-producing isolates revealed the presence of several hypothetical genes encoding for lipolytic enzymes, including outer cell-bound enzymes, predicted through the application of machine-learning tools. These natural isolates, containing cell-associated lipases, may therefore be of special interest for application as whole-cell biocatalysts.