Abstract: Extracellular phytase production by Candida tropicalis (GenBank Acc. No.JX532154) isolated from the gut of a freshwater teleost, Anabas testudineus has been investigated under solid-state fermentation. Among the different oilcakes [Groundnut (GOC), Sesame (SSC), Linseed (LOC), Mustard (MOC) and Soyabean (SOC)] evaluated as substrates, GOC supported maximum phytase activity (38.25±1.02 U/g) resulting 75.25% phytate degradation. Incubation for 8 days at 350C temperature with 70% moistening media of pH 6 revealed optimum phytase production. Maximum phytase activity was exhibited with 3% (v/w) inoculum size (43.45±1.14 U/g) and 70% initial moisture content (41.3±1.13 U/g). Glucose (2%, w/w) and ammonium nitrate (3%, w/w) supplementation resulted maximum phytase activity (39.45±1.12 and 38.75±1.06 U/g, respectively). Analysis of the fermented oilcake revealed that there was marginal increase (t-value significant at P < 0.05) in crude protein, lipid and minerals (Na, K, Ca, Mg, Zn, Fe, Cu, P, Mn) contents, and reduction of the anti-nutritional factors (e.g., crude fibre, tannin, phytic acid and trypsin inhibitor). The results indicated that application of the gut inhabiting yeasts in bio-processing of oilcakes merits further investigation for possible use of the plant feedstuffs as aqua-feed ingredients.