Harvesting

3.4.1 Solid State Fermentation


In case of solid state fermentation 100ml distilled water was added to the fermentated flasks and the flasks were shaken (150rpm) for half an hour. The contents were filtered by using wattman No. 1 paper and filtrate was used for citric acid analysis.

3.5 Optimization of parameters

3.5.1 Effect of pH

To find out the most suitable pH for the production of citric acid by Aspergillus niger, shake flask experiments were conducted at different initial pH values. 1M NaOH and 1M HCl were used to maintain the pH at 4, 4.5, 5.0, 5.5 and 6.0. The fermentation media adjusted to different pH volves were autoclaved, inoculated and incubated at 37oC for 3days.

3.5.2 Effect of inoculum size

To find out the most suitable inoculum size for the maximum production of citric acid the different quantity of inoculum was added in each flask as 2ml, 3ml, 4ml, 5ml, and 6ml. Inoculum size which gave maximum production will be selected for further parameters.



3.5.3 Effect of temperature

To find out the suitable temperature for the maximum production of citric acid the flask experiment will be conducted at different temperature as 25 oC

30 oC, 35oC, 40 oC and 45 oC.



3.6 Effect of Nitrogen supplements

Nitrogen constituent has a profound effect on citric acid production because nitrogen is not only important for metabolic reaction in the cells but it is also the basic part of cell proteins. Effect of 1% ammonium nitrate, ammonium sulphate and urea, Peptone, Yeast Extract were evaluated for the maximum production of citric acid. The nitrogen source, which gave maximum production of citric acid, was selected. Effect of different concentrations of that nitrogen source as 2%, 3%, 4%, 5%, and 6% were optimized for maximum citric acid production.