Starch-degrading enzyme activity of soil microbial community isolated from Makandura (NWP), Sri Lanka.

Abstract

Starch-degrading amylases derived from microbial sources have a greater industrial potential as it is economical when produced in large quantities. Amylases are predominant type of starchdegrading enzyme that accounts for around 25 % of the enzyme market. The present study aimed to determine the amylase activity of soil microflora isolated from Makandura (NWP), Sri Lanka. The enzyme activity of microbial community was measured at 24 hrs intervals up to 96 hrs and subsequently, for the purified bacterial colonies (Colony 20, 21, 37) that were selected by starch degrading Index (SDI), & which were grown in nutrient medium with 2 % starch at 37 ºC with 160 rpm. Further, the enzyme activity of the cultures was measured with continuous feeding of the fresh media. All the data were collected with three replicates for each, and the analysis was done by using R studio statistical software. The highest enzyme activity for the microbial community was observed in 24 hrs (143.07 mU/mL) while the lowest enzyme activity was observed in 96 hrs (15.21 mU/mL). The enzyme activity measured with the continuous feeding of the fresh medium had no effect in reviewing the declining trend of the enzyme activity suggesting that substrate was not a limiting factor. With respect to the enzyme activity of the purified colonies, the peak enzyme activity of 347.35 mU/mL was given by colony 37 at 72 hrs while the colony 20 and 21 gave 230.10 mU/mL and 230.23 mU/mL respectively in 48 hrs. The 60-80 % ammonium sulphate fractionation of clone 37 which was grown for 96 hrs gave the enzyme activity of 294.52 mU/mL which amounted to 22,089 mU from a 75 mL culture. Colony 37 which gave the highest enzyme activity can be used as a source of amylase-producing microbial strain after further characterization.