Production Optimization of a Thermostable Phytase from <em>Bacillus subtilis</em> SP11 Utilizing Mustard Meal as a Substrate

Phytate, an antinutritional molecule in poultry feed, can be degraded by applying phytase, but its use in developing countries is often limited due to importation instead of local production. Here, inexpensive raw materials have been used to optimize the production of a thermostable phytase from an indigenous strain of Bacillus subtilis SP11 that was isolated from a broiler farm in Dhaka. SP11 was identified using 16s rDNA and fermentation of phytase was optimized using Plack-ett-Burman design and response surface methodology, revealing that three substrates including the raw material mustard meal (2.21 % w/v) cause maximum phytase production of 436 U/L at 37oC and 120 rpm for 72 hours, resulting in a 3.7-fold increase compared to unoptimized media. The crude enzyme showed thermostability up to 80oC (may withstand the feed pelleting process) with an optimum pH 6 (near crop and small intestine pH), while retaining 96% activity at 41oC (body temperature of the chicken). In vitro dephytinization demonstrated its applicability, releasing 1956 µg of inorganic phosphate per g of wheat bran per hour. This phytase has the potential to reduce the burden of phytase importation in Bangladesh by making local production and application capable, contributing to sustainable poultry nutrition.