Degradation of phytic acid content in soy pulp by bacillus thuringiensis SP4 through solid-state fermentation

Chan, Onn Kei (2018) Degradation of phytic acid content in soy pulp by bacillus thuringiensis SP4 through solid-state fermentation. Master dissertation/thesis, UTAR.

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Abstract

Fresh soy pulp is a loose material consisting good source of nutrients and was given merit to use as an excellent protein source in the animal feed industry. The high phytate content in the soy pulp has become one of the prime concerns for livestock consumptions, as the digestion of phytic acid is unfavorable for monogastric and agastric aquatic animals. The undigested phytate is believed to inhibit the bioavailability of micronutrients and act as an anti-nutritional agent. Present study was intended to produce low-phytate soy pulp through solid-state fermentation (SSF) with locally isolated Bacillus thuringiensis SP4. A total of 10 phytic acid degrading bacteria were isolated using rice bran extract (RBE) and soy pulp extract (SPE) agars. Isolate SP4, which was identified as Bacillus thuringiensis SP4, was distinguished one among others by decreasing 62.65% of the phytic acid content in soy pulp after 72 hours SSF. Through 2-level full factorial design, the significant factors affecting the reduction of phytic acid were inoculum size and initial moisture content. Subsequently, 3-level factorial design was employed to determine the optimal conditions of the screened factors and maximal phytic acid reduction was achieved 86.40% at run no. 20. The linear regression model was then validated iii through confirmatory runs and less than 6% error rates reflected the model was adequate for predicting the total phytic acid reduction in SSF. The fermented soy pulp was analyzed by scanning electron microscopy (SEM) to observe the morphology and fourier transform infrared (FTIR) analysis to predict the changes of functional groups. Conclusively, the presented results suggested soy pulp could be used as in situ source of phosphohydrolases, where high nutritional values can be expected from the fermented low-phytate soy pulp. The prospects of using soy pulp as low-cost substrate in bioprocess also serve as an alternative for soybean waste management.

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