Aims: To optimize selected process variables for oxalic acid production by Aspergillus niger using Response surface methodology.
Study Design: Central composite design.
Place and Duration of Study: Department of Microbiology, University of Port Harcourt, Rivers State, Nigeria.
Methodology: Three media for the study was set up- algal biomass medium, sucrose medium and mixture of both algal biomass and sucrose medium. Inoculum of Aspergillus niger was prepared and subsequently inoculated into media for oxalate production by submerged fermentation. The oxalate produced after 14 days was determined by the catalytic effect of oxalic acid on the redox reaction between rhodamine B and dichromate.
Results: The predicted conditions of pH 6.838, temperature 35ºC and substrate algal biomass and sucrose with oxalic acid production of 8.618 g/L were reported in the study. This slightly varies with the experimental conditions of pH 6, temperature 35ºC, algal biomass and sucrose mixture and oxalic yield of 12.12 g/L. The R2 value of 0.968 validates the model and adjusted R2 of 0.9449 shows that the model is significant.
Conclusion: The study shows the feasibility of using the response surface methodology (RSM) in optimizing pH, temperature and substrate for the production of oxalic acid (g/l). It further shows the increased possibility of algal biomass as alternative feedstock for production of organics.
Oxalic acid production by Aspergillus niger: an oxalate-non-producing mutant produces citric acid at pH 5 and in the presence of manganese