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INFLUENCE of PARTICLE SIZE on CITRIC ACID PRODUCTION by Aspergillus niger USING RICE CHAFF and SESAMUM OIL CAKE as SUBSTRATES

S M Gopinath

This study mainly pertains to the variations on citric acid production brought about by ETGP12 and ETGP18 strains of Aspergillus niger at different particle size of rice chaff and sesamum oil cake as substrates. Initially the substrates were ground and were sieved through sieves as having different sizes 2, 4 and 6 mm and substrate media of each particle size were separately used. The results showed that the yield of citric acid in ETGP12 strain of Aspergillus niger increased with increase in particle size as substrate up to 4 mm giving a maximum yield of 97.5 and 102.4 g/kg from sesamum oil cake and rice chaff, respectively and the yield decreased at particle sizes below 2 mm. Similar kind of observations were seen in the ETGP18 strain of A. niger giving a maximum of 71.3 and 76.3 g/kg yield at particle size 4 mm of sesamum oil cake and rice chaff ,respectively. It was also found that at the particle size of 2 mm , the conversion of sugar into citric acid was also observed and found less compared to the particle size of 4 mm of substrate