Selectivity of Candida antarctica B lipase toward fatty acid and (Iso)propanol substrates in esterification reactions in organic media

Improved method for qualitative screening of lipolytic bacterial strains

Esterases and lipases are lipolytic enzymes that catalyse the hydrolysis of triacylglycerols, Determination of lipolysis on agar plates is a simple approach to determine lipase or esterase action, but visual evaluation of lipolysis is frequently difficult in practice. Therefore, the aim of this work was to improve the efficiency of lipolysis visualization in tributyrin agar (mTBA) by adding calcium and/or magnesium ions in the screening of lipolytic microbial strains. Lipolytic activity was evaluated in mTBA using the well diffusion technique, where a clear zone around the inoculated wells indicated lipid hydrolysis. Results suggest that the addition of 2.5 mM calcium and 5.0 mM magnesium was the best combination of ion addition to TBA. Lipolytic activity increased the clearing zone up to 38% more than without the addition of ions and the clear zone was clearly observed. The mTBA plate was used with culture collection microbial strains, as well as with a collection of soil microorganisms, to identify lipase producers. The addition of calcium and magnesium ions can provide an easier screening procedure for selection of lipolytic bacterial strains. •A modified tributyrin agar for screening of lipolytic bacteria was prepared by adding calcium and magnesium ions.•The modified TBA agar was tested with control bacterial strains, and, based on the results, 2.5 mM Ca and 5.0 mM Mg ions were added in the mTBA.•mTBA was validated with environmental bacterial strains for screening of lipolytic activity.

Process engineering and optimization of glycerol separation in a packed-bed reactor for enzymatic biodiesel production

A process model for efficient glycerol separation during methanolysis in an enzymatic packed-bed reactor (PBR) was developed. A theoretical glycerol removal efficiency from the reaction mixture containing over 30% methyl esters was achieved at a high flow rate of 540 ml/h. To facilitate a stable operation of the PBR system, a batch reaction prior to continuous methanolysis was conducted using oils with different acid values and immobilized lipases pretreated with methyl esters. The reaction system successfully attained the methyl ester content of over 30% along with reduced viscosity and water content. Furthermore, to obtain a high methyl ester content above 96% continuously, long-term lipase stability was confirmed by operating a bench-scale PBR system for 550 h, in which the intermediates containing methyl esters and residual glycerides were fed into the enzyme-packed columns connected in series. Therefore, the developed process model is considered useful for industrial biodiesel production.