A potential fungal strain producing extracellular $eta$-glucosidase enzyme was isolated from sea water and identified as Aspergillus sydowii BTMFS 55 by a molecular approach based on 28S rDNA sequence homology which showed 93% identity with already reported sequences of Aspergillus sydowii in the GenBank. A sequential optimization strategy was used to enhance the production of $eta$-glucosidase under solid state fermentation (SSF) with wheat bran (WB) as the growth medium. The two-level Plackett-Burman (PB) design was implemented to screen medium components that influence $eta$-glucosidase production and among the 11 variables, moisture content, inoculums, and peptone were identified as the most significant factors for $eta$-glucosidase production. The enzyme was purified by $(NH_4)_2SO_4$ precipitation followed by ion exchange chromatography on DEAE sepharose. The enzyme was a monomeric protein with a molecular weight of ~95 kDa as determined by SDS-PAGE. It was optimally active at pH 5.0 and $50^{circ}C$. It showed high affinity towards eNPG and enzyme has a $K_m$ and $V_{max}$ of 0.67 mM and 83.3 U/mL, respectively. The enzyme was tolerant to glucose inhibition with a $K_i$ of 17 mM. Low concentration of alcohols (10%), especially ethanol, could activate the enzyme. A considerable level of ethanol could produce from wheat bran and rice straw after 48 and 24 h, respectively, with the help of Saccharomycescerevisiae in presence of cellulase and the purified $eta$-glucosidase of Aspergillussydowii BTMFS 55.