Property characteristics and biotechnological significance of bacterial esterases

Na podstawie informacji literaturowych zaprezentowano aktualną wiedzę o właściwościach biokatalitycznych esteraz bakteryjnych oraz metodach ich modyfikacji. Uwzględniając informacje o specyficznej aktywności esteraz, opisano różnice między nimi a lipazami. Zwrócono uwagę na ich specyfikę substratową oraz na uwarunkowania związane ze środowiskiem reakcji ze szczególnym uwzględnieniem zawartości wody. Przedstawiono również przykłady potwierdzające znaczenie biotechnologiczne esteraz w kształtowaniu cech smakowo-zapachowych serów, wina, a także w produkcji niektórych składników żywności, farmaceutyków lub kosmetyków. Wskazano na współczesne możliwości doskonalenia cech genetycznych bakterii w kierunku poprawy wydajności syntezy esteraz oraz ich specyficzności ważnej w praktyce.Esterases represent a diverse group of hydrolases catalyzing the cleavage and formation of ester bonds. They are widely distributed in animals, plants and microorganisms. Beside lipases, a considerable number ofmicrobial esterases have also been discovered and overexpressed. Comparisons between esterases and lipases reveal remarkable sequence similarities, despite radically different substrate specificities and physiological functions. Esterase can perform ester hydrolysis and substrate transesterfication reactions. They prefer water-soluble substrates and can only hydrolyze triglycerides composed of short-chain fatty acids. Esterases display high regio- and stereo-specificity, require no co-factors and are usually stable and active in organic solvents. These make them attractive in important industrial and medical applications in the production of optically-pure compounds in fine chemical synthesis, including the metabolic processing of drugs and antimicrobial agents. Esterases originate from mesophilic bacteria as well as from cold-adapted or thermostable organisms. This paper focuses on the considerable amount of research directed at defining the accumulation of esters during fermentation and their contribution to aromas in foods and beverages. From this research, it is obvious that esters are extremely important for the aroma profile of fermented beverages and various dairy products. Based on the available information and a literature search, it is also clear that lactic acid bacteria in fermented beverage and dairy products possess an extensive collection of ester-synthesizing and hydrolyzing activities. This review also presents the major esters reported in wine and cheese and the enzymes responsible for their hydrolysis and synthesis. Ester impact on fermented product aroma and formation during primary and malolactic fermentation was also evaluated. Moreover, the potential applications of current knowledge of esterases are also described. Attention is also paid to the possibility of improving the genetic characteristics of bacteria to improve the synthesis efficiency and specificity of important esterase enzymes. Metabolic engineering is expected to have a significant impact on ester biosynthesis by microorganisms. Genetic engineering offers the potential for further control of wine/cheese aroma, including inactivation or over-expression of esterase and alcohol acetyltransferase genes. As an interesting alternative, GRAS/food-grade expression systems or directed evolution, which are more acceptable for use in food products, are also mentioned