Protopectinase Production by Geotrichum klebahnii in Fed-Batch Cultures with a Synthetic Medium

ZAPATA ZAPATA, ARLEY DAVID; CAVALITTO, SEBASTIÁN FERNANDO; HOURS, ROQUE ALBERTO

Saltillo, Mexico

Congreso; Segundo Congreso Internacional Food Science and Food Biotechnology in Developing Countries; 2006

Sociedad Mexicana de Biotecnología y Bioingeniería

Protopectinases (PPases) constitute a heterogeneous group of extracellular enzymes able to release soluble pectin from insoluble protopectin in plant tissues. G. klebahnii (ATCC 42397) produces PPase-SE with endopolygalacturonase activity. PPase-SE has been used for pectin extraction and maceration of plant tissues to obtain single-cell foods. Previous works indicated that enzyme production was growth associated and non-repressed by glucose. Specific enzyme activities achieved were higher in restricted (continuous) culture than in unrestricted (batch) cultures. According to these results, PPase-SE expression in fed-batch culture was studied. The microorganism was cultivated in a LH 210 bioreactor (Inceltech, France) with an initial volume of 3 L, at 30°C, with aeration (0.8 L/min) and agitation (550 rpm). pH and dissolved O2 were measured with a glass electrode and a polarographic electrode, respectively. Batch culture medium contained: glucose (limiting substrate, 10 g/L), urea (1.2 g/L), vitamin solution and Fe and Zn salts, initial pH: 2.8. Fed-batch cultures in glucose-limited conditions (reservoir medium composition was 4.4 ´ batch medium composition) were done with constant feeding flows (initial µ = 0.25, 0.20 or 0.15 h-1, decreasing with time), and also with an exponential feeding flow (µ = 0.20 h-1, constant). A batch process was used as reference of specific enzyme activity. Fed-batch cultures yielded higher enzyme activities than batch cultures, but an increment of final biomass was also observed. For this reason, specific activities were similar to those found in batch cultures except for the condition of constant alimentation flow with initial µ = 0.20 h-1. In this case, an increase of 20% in specific enzyme activity and 53% in YP/S (enzyme activity units per gram of glucose consumed) were observed. Considering the time for preparation and sterilization of the bioreactor, enzyme productivity was substantially higher in fed-batch cultures than in an equivalent amount of independent batch cultures. This result suggests that fed-batch culture is a favorable culture system for PPase-SE production.