Effect of C/N ratio and microelements on nutrient dynamics and cell morphology in submerged fermentation of Aspergillus giganteus MTCC 8408 using Taguchi DOE

This paper is concerned with the effect of individual Na+, K+, Mg2+ and Ca2+ ions upon the nutrient dynamics and cell morphology during submerged fermentation of Aspergillus giganteus MTCC 8408 in a medium containing ample soluble starch, corn steep liquor and proteose peptone supply. Nutrient dynamics was elucidated using Taguchi's DOE (design of experiment) L8 orthogonal array (OA) with carbon, nitrogen and four most influensive microelements at their assigned ratio namely; K+/Ca2+ and Mg2+/Na+. Scanning electron microscopy (SEM) was used to correlate the effect of selected factors on morphological changes and nutrient dynamics during submerged fermentation. At higher K+/Ca2+ ratio 4.78:1; the maximum growth was figured out in terms of dry weight, while the inhibition of dry weight production was observed at higher Mg2+/Na+ ratio 0.94:1 with enhanced intracellular afp production. At lower C/N ratio 27.4:1; filamentous form of growth was maintained with the hyphae being scarcely branched without bulbous cells. Membrane perturbation due to the induction of intracellular oxidative stress was noticed at higher C/N ration. Taguchi DOE resulted in afp yield per substrate utilized, Y p/s of 1.08 mg g-1 soluble starch utilized with gram dry cell weight (gdcw) of 23.9 g L-1 while afp yield per biomass utilized resulted, Y p/x of 1.12 mg afp gdcw-1 L-1 and biomass yield per substrate utilized, Y x/s of 1.195 gdcw g-1 L-1. The present study revealed an opportunity to develop a cost effective methods for cell propagation so as to yield effective inoculum levels towards mass production and formulation studies.