Isolation and Bioprocess Optimization of Halophilic and Alkaline Protease From Marine Streptomyces and Its Use As Contact Lens Cleaner

Abstract

<jats:title>Abstract</jats:title> <jats:p>In the present study, an alkaline protease was isolated from marine <jats:italic>Streptomyces</jats:italic> sp. GS – 3. The strain was isolated from the backwaters of Puthuvypeen, Kerala, and identified as <jats:italic>Streptomyces</jats:italic> sp. by polyphasic taxonomy. The media for protease production was optimized by response surface methodology (RSM) using the Box-Behnken model. The maximum yield (357 U/ml) was observed using wheat bran as substrate (5.5%), pH 5.5, and the incubation period of 9 days at 28 ᴼC. The optimum temperature and pH conditions for the maximum enzyme activity were 45 °C, and 9 respectively. The K<jats:sub>m</jats:sub> and V<jats:sub>max</jats:sub> values of the enzyme were determined as 5.88%, and 38.46 µmol l<jats:sup>− 1</jats:sup> min<jats:sup>− 1</jats:sup> mg<jats:sup>− 1</jats:sup>, respectively, using 1% casein as substrate. The enzyme was isolated by solvent extraction with acetone, and the crude enzyme was characterized by Sodium Dodecyl Sulphate Poly-Acrylamide Gel Electrophoresis (SDS-PAGE) and Circular Dichroism (CD) studies. The enzyme sustained at high temperature (50 °C for 6 h), and alkaline pH (10) conditions, and was active in the presence of metal ions, and organic solvents. The purified enzyme was inhibited by phenylmethylsulphonyl fluoride (PMSF) suggesting it belong to serine protease. Further to exploit its application, contact lenses were incubated with the enzyme solution, and the protein debris on it was found to be scrubbed at an optimum time of 60 minutes. Therefore, it increases the transmittance of the contact lens indicating its use as a potential contact lens cleansing agent.</jats:p>