No abstract

The present work emphasizes on citric acid production from distillery spent wash containing carbohydrates that has been tested to be novel and potential substrate. Pre-treatment of distillery spent wash was studied in an anaerobic digestion by suspended growth system under shifting hydraulic retention time and organic loading rate as well as physicochemical parameters. Fungi strain PN12 was applied for citric acid production using raw post methanated waste (treated spent wash). A potent fungus was identified by molecular characterization (18S rRNA). To find phylogenetic relatedness gene sequence of potent culture PN12 has been compared with other sp. gene sequences registered at database of NCBI and the phylogenetic tree was created by software. For enhancement of citric acid production was carried out in different nutritional and environmental parameters such as inoculum size (2 to 10 %), incubation period (24 to 144 h), pH (2 to 7), temperature (25 to 37°C), nitrogen source (organic and inorganic 0.1 g/L), phosphorus source (0.1g/L). The detection of enzymes activities specified that the pathway of pyruvate carboxylation enhanced, which proposed carbon flux to citric acid it was reorganized in strains. Analysis of biosynthesized products by UV/Vis spectrophotometer and HPLC. Initial sugar and consumed sugar determined by DNSA method and also estimated cell dry weight.

Distillery spent wash is an unwanted residual liquid waste generated during alcohol production. It is a potential source for production of different industrially important products. Distillery spent wash is dark colored and has many organic compounds as a waste. In this experiment, removal of color and organic compounds was carried out by anaerobic treatment. The treated spent wash was utilized for citric acid production with the help of microorganisms. The current study was performed with the treated spent wash which was applied for high level of citric acid production by a mutant strain of Aspergillus fumigatus PN12. The parent strain Aspergillus fumigatus PN12 was mutagenized by UV exposure to enhance citric acid production. After UV exposure investigation, mutant strain was selected for optimization and statistical method. The best citric acid production obtained was, 26.45 g/L at 30 ℃ with pH 6.0, 0.1 g/L of KH2PO4 and (NH4)2SO4 under OFAT. Under RSM optimization, maximum citric acid production was achieved as 30.89 g/L. Thus, the process optimization through the statistical approach resulted in a 1.16-fold enhancement in citric acid production as compared to that of the OFAT parametric conditions. Citric acid producing enzymes such as aconitase, NAD+-isocitrate dehydrogenase and NADP+ isocitrate dehydrogenase was studied. Maximum activity (U/mg) of aconitase (3.19±0.023), NAD+-isocitrate dehydrogenase (3.0±0.15) and NADP+ isocitrate dehydrogenase (2.91±0.17) was observed at 96 h. The present study can conclude that spent wash is potential source for citric acid production. Utilization of mutant strain of Aspergillus fumigatus PN12 is beneficiary for large scale industrial fermentation and citric acid production.