Studies were conducted on the production and extraction of exo-polygalacturonase (PG) in solid-state fermentation (SSF) using orange bagasse (Ob) and molokhia stalks (Ms) as a new solid support by Penicillium pinophlilum Hedg 3503 NRRL. The parameters affecting PG production under SSF were optimized. The maximum PG activity of ~ 3270 U/ g dry solid substrate was obtained from P. pinophlilum Hedg 3503 NRRL grown for 7 days on Ob and Ms in the ratio 1:3 (w/w), moistened with distilled water at 68.2% initial moisture content. Highest enzyme titers occurred in SSF without added nutrients, indicating nutrient sufficiency of the Ob and MS mixture to sustain growth and a high level of pectic substances which induced PG production. The extraction of PG from the fermented biomass was optimized. Among the various solvents tested, the maximum level of enzyme activity was achieved when acetate buffer (0.05 M; pH 5.0) was used. The optimum volume of buffer was 50 mL, an extraction time of 60 min was sufficient to extract most enzyme, which yielded 3269.6 U/ g dry solid substrate of enzyme activity. Repeated washes under the optimum conditions showed that most of the enzyme (about 98%) was recovered in three repeated extractions. Moreover, 68.9% of total activity was achieved in the first wash.
Exo-polygalacturonase; Solid-state fermentation; Solid substrate
