Xylanase production by the thermophilic mold Humicola lanuginosa in solid-state fermentation.
Among the lignocellulosic substrates tested, wheat bran supported a high xylanase (EC 3.2.1.8) secretion by Humicola lanuginosa in solid-state fermentation (SSF). Enzyme production reached a peak in 72 h followed by a decline thereafter. Enzyme production was very high (7832 U/g of dry moldy bran) when wheat bran was moistened with tap water at a substrate--to--moistening agent ratio of 1:2.5 (w/v) and an inoculum level of 3 x 106 spores/10 g of wheat bran at a water activity (aw) of 0.95. Cultivation of the mold in large enamel trays yielded a xylanase titer comparable with that in flasks. Parametric optimization resulted in a 31% increase in enzyme production in SSF. Xylanase production was approx 23-fold higher in SSF than in submerged fermentation (SmF). A threshold constitutive level of xylanase was secreted by H. lanuginosa in a medium containing glucose as the sole carbon source. The enzyme was induced by xylose and xylan. Enzyme synthesis was repressed beyond 1.0% (w/v) xylose in SmF, whereas it was unaffected up to 3.0% (w/w) in SSF, suggesting a minimization of catabolite repression in SSF.
Kamra
Pankaj
P
Department of Microbiology, University of Delhi South Campus, New Delhi 110021, India.
Satyanarayana
T
T
D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000379:methods*; D004043:Dietary Fiber / Q000382:microbiology*; D043364:Endo-1,4-beta Xylanases / Q000096:biosynthesis*; D004789:Enzyme Activation; D005285:Fermentation / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D013149:Spiroplasma / Q000201:enzymology*; D013379:Substrate Specificity; D013696:Temperature; D014994:Xylose / Q000378:metabolism*
D004043:Dietary Fiber; D014994:Xylose; D043364:Endo-1,4-beta Xylanases