Production of citric acid from starch-hydrolysate by Aspergillus niger.
The present investigation explored the possible use of a rarely used agro-industrial by-product, maize starch-hydrolysate, for economic production of citric acid. To achieve this, seventeen strains of Aspergillus niger were screened for their capacity to produce citric acid using starch-hydrolysate as a substrate. The most efficient strain, ITCC-605 was selected for further improvement in citric acid content by mutation. Mutants developed by treatment with EMS and UV, singly and in combination, produced citric acid in the range of 0.51-64.7 g kg(-1) of glucose consumed. The mutant UE-1 produced the maximum citric acid which was about 130 times more than that produced by the parent strain, ITCC-605. For further increase in citric acid production from this substrate, the cultural conditions were optimized: concentration of starch-hydrolysate, 15% (glucose equivalent); ammonium nitrate, 0.25%; KH2PO4, 0.15%; nicotinic acid, 0.0001% and initial pH of 2.0. Under these conditions, the mutant strain UE-1 yielded 490 g citric acid kg(-1) of glucose consumed in 8 days of incubation at 30 degrees C. The productivity of 341 mgl(-1)h(-1) corresponded to 49% substrate conversion to citric acid.
Mourya
S
S
Division of Microbiology, Indian Agricultural Research Institute, New Delhi. sm_micb@iari.ernet.in
Jauhri
K S
KS
D001234:Aspergillus niger / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism*; D003470:Culture Media; D013213:Starch / Q000378:metabolism*; D003313:Zea mays / Q000737:chemistry
D003470:Culture Media; D019343:Citric Acid; D013213:Starch