Glucose isomerase production on a xylan-based medium by Bacillus thermoantarcticus

2009-01-15
Çalık, Pınar
Angardi, Vahideh
Haykir, Nazife Isik
BOYACI, İSMAİL HAKKI
Effects of medium components on intracellular glucose isomerase (GI) production were investigated by Bacillus thermoantarcticus. The highest GI activity was obtained as 1630 U dm(-3) in the medium containing (g dm(-3)): 10.6, birchwood-xylan: 5.6, yeast extract: 5.9 (NH(4))(2)SO(4) at T = 55 C in 33 cm(-3) shake-flasks. When birchwood-xylan was replaced with oat spelt- or beechwood-xylan, GI activity decreased to 1372 and 1308 U dm(-3). respectively. Effects of pH at uncontrolled-pH (pH(UC) = 6.0) and controlled-pH (pH(C) = 6.0) operations, and oxygen transfer at the all, inlet rate of 0.5vvm and agitation rates of 300, 500 and 700 min(-1), were investigated in 3.0 dm(-3) bioreactor system with 1.65 dm(3) working Volume in the designed medium. The highest GI activity was attained at 500 min(-1), 0.5 vvm, pH(UC) = 6 as 1840 U dm(-3) where cell concentration was 2.3 g dm(-3). The use of agricultural waste xylan, as the carbon source resulted in concomitant production of xylanase and GI. The highest xylanase activity was attained as 9300 U dm(-3) at 500 min(-1) and 0.5 vvm. K(L)a varied between 0.008-0.033 s(-1) whereas the highest oxygen Uptake Fate was 0.002 mmol dm(-3) s(-1). Initially biochemical reaction limitations were effective: thereafter, mass transfer resistances became more effective,