UTILIZATION OF INDUSTRIAL WASTE (CHEESE WHEY) FOR THE BIOSYNTHESIS OF β-GALACTOSIDASE

Abstract

The dairy industry is associated with the production of contaminated waste water. The whey disposal remains a serious pollution problem for dairy industry, particularly in developing countries. Direct disposal of whey in the environment creates serious pollution problems, it destroys the physical and chemical structure of soil which decreases the crops yield and if discarded in water bodies, it reduces the aquatic life. The best solution to this environmental problem is the enzymatic hydrolysis of whey by using β-galactosidase which catalyses the hydrolysis of lactose (main constituent of whey) into its basic monomers, glucose and galactose. β-galactosidase can be obtained from different sources like plants, animals and microorganisms whereas bacterial β-galactosidase is generally regarded as safe. The basic aim of present research is to investigate the utilization of dairy industrial waste (cheese whey) as a substrate for the biosynthesis of β-galactosidase to convert environmental waste into useful biomaterial from a noval β-galactosidase producing bacterial isolate from Antarctica. Two hundred and thirty five isolates were obtained from five samples (ice, water and microbial mats) collected from different sites of Antarctica and screened for their ability to produce β-galactosidase by using X-gal. A total of 61 bacterial isolates which turned blue on X-gal were then cultured in R2 medium and Marine medium aseptically at 10˚C for one month. The most potent bacterial isolates were identified using a polyphasic taxonomical approach. Cells were found strictly aerobic, Gram negative, rod shaped, motile and formed creamy white, half transparent colonies. Growth occurred at 4°C to 28°C with an optimum at 20°C, with 0 – 5.0 % (w/v) NaCl (optimum at 0 - 1.0 %) and at pH 4.0 – 11.0 (optimum at pH 7.0 - 9.0). The major fatty acid was C18:1 ω7c. Respiratory quinone was ubiquinone 10 (Q-10). The DNA G+C content was 60.7 %. The polar lipids were phosphatidylglycerol, phosphatidylethanolamine and phosphatidylmethanolamine in addition to three unidentified lipids, one unknown glycolipid, and five unidentified phospholipids. Comparative analysis of 16S rRNA gene sequences showed highest sequence similarity (98.1 %) to Pararhizobium giardinii H152T, P. herbae CCBAU 83011T, and “P. polonicum” F5.1T. In silico average nucleotide identity (ANI) and genome-to-genome distance calculator (GGDC) showed 81.1 % identity (ANI) and 22.6 % identity (GGDC) to the closest relative, “P. polonicum” F5.1T. On the basis of phenotypic, phylogenetic, genomic and chemotaxonomic data, the two strains xii represent a novel species of the genus Pararhizobium, for which the name Pararhizobium antarcticum sp. nov. is proposed. The type strain is NAQVI 59T LSRP00000000 (=DSMZ 103442T = LMG29675T). Strains NAQVI-58 and NAQVI-59T showed the highest enzyme production (0.21 U/ml) for strain NAQVI-58 and (0.33 U/ml) for strain NAQVI-59 with cheese whey as a substrate at pH (7), 28 ˚C and after 48 hours of incubation respectively. In this study, a new Pararhizobium sp. is discovered by using dairy industrial waste cheese whey as a substrate which is further used for the production of β-galactosidase.