Improved β-galactosidase Secretion in Fresh Water Fungi through Cultural Optimization

The wide range of applications of β-galactosidase has made it a candidate enzyme of study for improved yield. Most studies focused on expressing this enzyme in expressible vector(s) while sources of this enzyme are rarely investigated. Aquatic habitats harbor arrays of microorganisms that can participate in demineralization, nutrient restoration, circulation and hence confer significant properties on the habitats and significantly influence microbial interactions and metabolism. In view of this, aquatic fungal isolates were qualitatively and quantitatively screened for intracellular and extracellular β-galactosidase production. Four fungal isolates tagged SB01 and SC02 from stream identified as Aspergillus oryzae and Aspergillus niger and SC01 and SA01 from pond identified as A. oryzae and A. niger were studied. β-galactosidase gene was successfully amplified from the four isolates and their enzyme production levels were further studied. All the isolates showed considerably higher extracellular secretion than the intracellular synthesis on glucose-based medium. The production level was probed by xylose supplementation but surprisingly, the intracellular synthesis was higher than the extracellular secretion for all the isolates. In an attempt to boost the enzyme production, temperature was varied and 25 °C showed improved β-galactosidase synthesis and secretion than the 30 °C. This study revealed these filamentous fungi as candidates for β-galactosidase production and broaden the understanding of harnessing microorganisms from an aquatic reservoir for bio-production, and more importantly, revealed the intracellular accumulation of the enzyme as a bottleneck for industrial production. HIGHLIGHTS The wide range of applications of β-galactosidase has made it a candidate enzyme of study for improved yield Most studies focused on expressing this enzyme in expressible vector(s) while sources of this enzyme are rarely investigated Aquatic fungal isolates were qualitatively and quantitatively screened for intracellular and extracellular β-galactosidase production All the isolates showed considerable higher extracellular secretion than the intracellular synthesis on glucose-based medium, and vice-versa on xylose-supplemented medium, with the highest β-galactosidase synthesis and secretion efficiency occurring at 25 °C in both instances This study revealed these filamentous fungi as candidates for β-galactosidase production and broaden the understanding of harnessing microorganisms from an aquatic reservoir for bio-production GRAPHICAL ABSTRACT