PENGARUH MODIFIKASI KIMIA TERHADAP STABILITAS TERMAL ENZIM a-AMILASE DARI BAKTERI ISOLAT LOKAL Bacillus subtilis ITBCCB148

Yandri A.S., Cynthia Radiman, Muliawati Sindumarta, Soetijoso Soemitro

Abstract


The objective of the research is to study effect of chemical modification for the thermal stability of a local
bacteria isolate Bacillus subtilis ITBCCB148 a-amylase by chemical modification with activated-PEG. The
purified enzyme was modified with either cyanuric chloride polyethylene glycol (CC-PEG) or pnitrophenolcarbonate-
polyethylene glycol (NPC-PEG). The amount of modified lysin residues was indicated
by modification degree determined with trinitro benzene sulfonic acid (TNBS). The success in chemical
modification of the enzyme was evaluated by comparing the thermal stability of the enzyme before and after
modification. The results showed tha modification of the enzyme with CC-PEG resulted in modified
enzymes with modification degrees of 23, 63, and 67%. The thermal stability of the modified enzymes with
modification degrees of 23, 63, and 67% at 60°C was indicated by t1/2 value of 30.7 minute, ki value of 0.019
minute-1, DGi value of 104.2 kJ mol-1; t1/2 value of 41.3 minute, ki value of 0.016 minute-1, DGi value of 104.7
kJ mol-1; and t1/2 value of 47.6 minute, ki value of 0.015 minute-1, DGi = 104.9 kJ mol-1 respectively.
Modification of the enzyme with NPC-PEG resulted in modified enzymes with modification degrees of 56,
76, and 89%. The thermal stability of the modified enzymes with modification degrees of 56, 76, and 89% at
60°C was indicated by t1/2 value of 30.3 minute, ki value of 0.018 minute-1, DGi value of 104.4 kJ mol-1; t1/2
value of 49.6 minute, ki value of 0.011 minute-1, DGi value of 105.7 kJ mol-1; and t1/2 value of 59.1 minute, ki
value of 0.009 minute-1, DGi = 106.3 kJ mol-1 respectively.
Keywords: a-amylase, thermal stability, Bacillus subtilis ITBCCB148

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