CITRIC ACID FERMENTATION OF HYDROLYSED SWEET POTATO STARCH BY ASPERGILLUS NIGER

Abstract

The present study deals with the screening of Aspergillus niger from soil for citric acid
production by submerged fermentation. A. niger IIB-A6 produced 23.32±1.44 g/l citric acid.
Sweet potato starch was found as a better substrate compared to maize starch. The kinetic
parameters Yp/x (1.96 g/g cells), Qp (0.13 g/l/h) and qp (0.014 g/g/h) were 8-10 fold higher with
sweet potato starch than the maize starch. Sugar conc. (150 g/l), incubation period (168 h) and
initial pH (6.0) were optimized. The maximum citric acid production obtained during the
course of study was 28.40±1.07 g/l. Sugar consumption and dry cell mass were 121.33±0.91
and 14.29±0.88 g/l, respectively. The mycelia were small pellets.