Triacylglycerol biodegradation experiment in marine environmental conditions: definition of a new lipolysis index

An experiment on the biodegradation of dissolved triacylglycerol (TG) by a natural Antarctic bacterial community was performed at in situ temperature, in the dark. The lipid classes and their metabolites resulting from the TG degradation were identified and quantified by TLC/FID Iatroscan analysis. TG was hydrolysed rapidly by bacteria (K=−0.22 d−1), whereas metabolites were accumulated at different rates. An increase of phospholipids (PL) was observed, related to the growth of bacteria. This experiment confirmed that in the marine environment, diglycerides (DG), monoglycerides (MG) and free fatty acids (FFA) are released by the hydrolysis of acyl-lipids. We define the Lipolysis Index (LI) as the ratio of the sum of the metabolites resulting from the acyl-lipid degradation to the sum of the acyl-lipids present in the medium. We propose to use this lipolysis index (LI) as a new tool which characterises the degradation stage of labile organic matter in natural sea water samples.