Degradación de glicerol por la vía reductiva en P. pentosaceus CAg aislado de cerveza

VIZOSO PINTO, M. G.; PASTERIS, S. E.; STRASSER DER SAAD, A. M.

Tafí del Valle, Tucumán, Argentina

Jornada; XVIII Jornadas científicas de la Sociedad de Biología de Tucumán; 2001

Sociedad de Biología de Tucumán

Lactic acid bacteria (LAB) may produce flaws with the formationof metabolites. During alcohol fermentation, yeastproduces glycerolin high amounts. If LAB are capable of using it as a C source,they may produce changes in thequality of beer. We isolated P.pentosaceus CAg during the malting stage. The cultures were grownin modifiedMRS-broth with glucose and/or glycerol in microaerophilicconditions. We have followed the dynamics of growthandformation of fermentation products. The activities of the enzymesinvolved in the possible metabolic pathwayswere measured. Thisstrain is able to grow on glycerol as the only C source but with alower m (h-1) than onglucose. With both substrates, growth is diauxic;after glucose consumption glycerol is consumed in the samepercentageas without glucose. The main products detected were DandL-lactate, acetate, 1,3-propanediol, diacetyland 2,3-butanediol.We did not find the oxidative pathway in any of the cases. In allcell-free extracts we found 1,3-PDDH activity whereas GK activitywas only detected in extracts from glycerol medium. These resultssupportedthe fermentation balance we found. This is the 1sttime that the gliceroldehidratase pathway, leading to theundesirableproduction of acrolein, is described in a homofermentativeLAB.