Effect of culture medium on polymer production and temperature on recovery of polymer produced from newly identified Rhyzopus oryzae ST29

Abstract

Thermotolerant fungal isolate ST29 was identified by observing on cell morphology and molecular technique based on internal transcribed spacer (ITS) gene to be Rhizopus oryzae. Among four culture media tested, the strain exhibited the highest growth in yeast malt extract (YM) medium (4.87 g/l), followed by Sabouraud dextrose broth (SDB) (4.25 g/l), potato dextrose broth (PDB) (4.10 g/l) and palm oil mill effluent (POME) (3.29 g/l), respectively, after 4 days cultivation at 45oC. However, the strain was found to produce polymer only in POME medium at 45oC, but not in the three synthetic media tested. Effect of temperature on separation of the biopolymer produced by this fungal strain was studied by incubating the culture broth in water bath with temperatures in the range of room temperature to 70oC. The biopolymer was recovered by filtration, centrifugation, and precipitation by adding 4 volumes of 95% ethanol, then freeze-drying. These temperatures therefore had no influence on the biopolymer yields (5.58-5.78 g/l) or on biomass yields (2.90-3.29 g/l)