Abstract
Aqueous extraction process was optimized to reduce endotoxins from mixed substrate (1:1) for further phytase production by Rhizopus oryzae in solid state fermentation. 23 factorial design of experiment was combined with either a back-propagation artificial neural network (ANN) or the response surface methodology (RSM) for optimizing the process variables (length of extraction time, substrate loading and different pH of extraction solvent) to predict and simulate phytase production and phosphorus release. ANN was found to be a more powerful tool than RSM, for modeling and optimizing variables for the aqueous extraction process and can be used for predictive simulations of a process. A 2.37-fold increase in phytase production (37.65 U/gds) was achieved at the model predicted optimum concentration of extraction time of 29.78 min, substrate loading at 11.04 g and pH of extraction solvent at 7.1 as compared to the phytase yield in untreated substrate (15.91 U/gds). Moreover, the reduction in phytic acid after aqueous extraction of substrates was validated after high performance liquid chromatography (HPLC) characterization study. The results suggest that aqueous extraction process can be used efficiently for reducing the endogenous anti-nutritional factors from substrates eventually leading to enhanced phytase yield. Key words: Rhizopus oryzae, high performance liquid chromatography (HPLC), phytic acid, solid state fermentation, optimization.
Highlights
Oil cakes/meals and agricultural by-products have long been considered as the most inexpensive and high energy rich substrates for fermentation industry
PBD was used for investigating the relative importance of seven independent factors for phytic acid reduction from substrate to be utilized for phytase production
It was evident that A, D and E enhanced the phytase production at their low level whereas, high level of B, C, F and G supported high phytase yield
Summary
Oil cakes/meals and agricultural by-products (various cereal brans and husks) have long been considered as the most inexpensive and high energy rich substrates for fermentation industry. Effective utilization of these residues helps to curb looming environmental pollution due to its disposal and paves the way for solid waste management and minimizes the initial capital costs for the production processes. Despite being a rich source of dietary proteins and fibres, presence of various endogenous antinutrients such as phytic acid, linamarin (a cyanogen) and linatine (an antipyridoxine factor) in linseed meal is the important factor limiting its use as value added substrate for economical production of industrial enzymes and as feed supplement at higher levels (>3%). Klosterman et al (1967) showed that the linatine is a polar compound and can be extracted with water
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