Abstract
Solid-state fermentation (SSF) can divert food waste from landfills and produce high-value products. This study was aimed to investigate the feasibility of using SSF and optimize the conditions of production of phytase by Aspergillus ficuum from potato waste. Different parameters including pH of the potato waste, inoculum level, moisture content, incubation period, temperature, and supplementary nitrogen and carbon sources were evaluated. The results indicated that pH, inoculum level, and moisture content did not significantly vary phytase production. However, different incubation periods, incubation temperatures, nitrogen sources, and carbon sources changed the phytase production significantly. The ideal and economic conditions for phytase production consisted of a normal moisture content (79%) of potato waste, 1.0 ml inoculum size, and normal pH 6.1 at room temperature for 144 h incubation time. The highest phytase activity (5.17 ± 0.82 U/g ds) was obtained under the aforementioned optimized conditions. When (NH4)2SO4 was used as a nitrogen source in the substrate, the phytase activity increased to 12.93 ± 0.47 U/g ds, which was a 2.5-fold increase compared to the control treatment. This study proposed a novel and economical way to convert food processing waste to highly valuable products and investigated the optimal conditions of the production of phytase during SSF in potato waste.
Highlights
Phytic acid is ubiquitous in nature and is the principal storage form of phosphorus in cereals, legumes, oilseeds, and nuts (Vohra and Satyanarayana 2003)
It means that pH did not have a significant influence on phytase production, which indicated that the metabolic activities of A. ficuum were not sensitive to the change in pH even though the maximum activity was achieved at pH 8.2
Phytase production was investigated by the optimization of different parameters and supplementing different carbon and nitrogen sources
Summary
Phytic acid is ubiquitous in nature and is the principal storage form of phosphorus in cereals, legumes, oilseeds, and nuts (Vohra and Satyanarayana 2003) It is known as a food inhibitor which can chelate micronutrients. Phytase is the primary enzyme that catalyzes the hydrolysis of phytic acid and releases inorganic phosphate, which improves the overall P digestibility by 25–30%, resulting from approximately 50% degradation of the cereal phytate (Jongbloed and Kemme 1990; Kemme et al 1997). This will alleviate phosphorus demand in animal feed, as P resource is approaching depletion. Phytase can be applied as cosmetic additives and plant nutrition (Koshy et al 2012; Gujar et al 2013)
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