The current study aimed to isolate xylanase-producing marine actinobacteria, which is a novel idea; ascribed to the challenges associated with the culturing of marine microorganisms. A total of 5 actinobacterial colonies were isolated from Kanyakumari marine sediments. Among them only one isolate, A1 indicated the elevated xylanase activity manifesting a zone of hydrolysis of around 20 mm during primary screening. On the other hand, secondary screening of A1 i.e., sugar estimation by 3,5-dinitrosalicylic acid method, resulted in A1 exhibiting 400 μg/ml of enzyme activity. The enzyme extracted from the isolate A1 also contained a protein concentration of 600 μg/ml. Physical and chemical mutation studies were carried out to over-express xylanase production. Chemical mutation involving the use of EDTA did not show a significant increase in xylanase production and thus, was not subjected to further analyses.
The isolate, A1 also showed a zone of hydrolysis of 28 mm in the physical mutation study and was named A'1.75. This zone was 8 mm more than the wild-type strain after UV-exposure for 75 min. A'1.75 also exhibited an enzyme activity of 600 µg/ml and protein content of 800 μg/ml. The potential isolate was identified as Streptomyces variabilis VITMUVB02 using 16S rRNA molecular sequencing. The molecular weight of the purified xylanase extracted from A1 and A'1.75 was found to be 25 kDa and 20 kDa, respectively. Fourier Transform Infrared spectroscopy (FT-IR) and High-Performance Liquid Chromatography (HPLC) analyses showed the mutagenic effect with the change in the spectral and functional groups.