Bioprospecting of pectinase enzymes from fungi
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Date
2013
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UAS Dharwad
Abstract
The present study was conducted to isolate, and characterize fungi from diverse
natural sources capable of producing pectinases. Based on the preliminary screening of 100
isolates, 48 isolates were found positive for pectinase production. Out of them, isolates
RBF96 (3.25), RC27 (3.21) and DLP51 (3.21) possessed the highest potency index values
compared to the reference strain Aspergillus niger MTCC1344 (2.99). Following the PCR
based molecular methods, the isolates were identified as Aspergillus niger, Aspergillus
oryzae and Penicillium citrinum respectively. Solid state fermentation (SSF) was carried out
using various locally available agro-wastes as the carbon source. Citrus peel was identified as
the most suitable substrate. The particle size of 2 mm, moisture level of 65 per cent,
incubation temperature of 35oC, inoculum level of 1 x 107 spores g-1 and the incubation time
of six days were found optimum. After purification the maximum specific activity of 83.06 U
μg-1 protein was obtained for polygalacturonase (PG) by A. niger RBF96 with seven fold
increase in purification. Similarly, about six folds and five folds increases in purification
were obtained for pectin lyase (PL) and pectin esterase (PE) in P. citrinum DLP51 and A.
oryzae RC27 respectively. The molecular weights of PG, PL and PE, as determined by SDSPAGE,
were 45 kDa, 37 kDa and 31 kDa respectively. The purified PG showed maximum
stability at pH 4.5, whereas, PL and PE showed at pH 6.5 and 5.0 respectively. The
temperature of 50oC was found optimum. The orange pulp treated with (PG+PL+PE) at 100
U resulted in the highest juice yield (90.17%) and the highest clarity (96.28%). Similarly, in
guava this treatment resulted in the highest juice yield (66.75%) and maximum clarity
(37.57%). The organoleptic evaluation proved that pectinases could be used to improve the
sensorial attributes of fruit juices.