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Rice flour as potential carbon source for production of phytase by <i>Aspergillus niger</i> F00735 strain

Bujna, E., Kukovics, F., Nguyen, Q. D., Rezessy-Szabó, J. M.
Acta alimentaria 2013 v.42 no.0 pp. 1-9
Aspergillus niger, carbon, corn flour, culture media, enzyme activity, octoxynol, phosphorus, phytases, phytic acid, rice flour, secretion, sodium nitrate, soy flour, submerged fermentation, surfactants, wheat
Production of phytase by <i>Aspergillus niger</i> F00735 strain in submerged fermentation was studied. The effects of various natural substrates with different phytate contents on secretion of extracellular phytase were investigated and the rice flour with about 5 mg g<sup>−1</sup> of phytic acid was found to be the best one. The repression effect of high levels of phytic acid or inorganic phosphorous in fermentation medium (corn flour, wheat grit, soy flour, etc.) on production of phytase was also observed. The optimal concentration of rice flour as main carbon sourc e was determined in combination with sodium nitrate. The maximal activity (≈1500 U l<sup>−1</sup>, 1.5 times higher than using basal medium) was achieved on the 7<sup>th</sup> day in media containing 7.12% (w/v) rice flour and 0.86% (w/v) sodium nitrate. Supplementation of fermentation medium with different surfactants such as Tween series (20, 40, 60, 65, 80, 85) and Triton X-100 up to 0.1% (w/v) had no significant effects on the secretion of phytase enzyme, meanwhile at concentrations higher than 0.2% (w/v), decrease in enzyme activity was observed.