Purification and properties of extracellular endoxylanases from alkalophilic thermophilic Bacillus sp.

Abstract

An extracellular endoglucanase (1,4-~-glucanohydrolas, EC 3.2.1.4) produced by Myceliophthora thermphila D-14 (ATCC 48104) has been purified to homogeneity by ammonium sulphate precipitation and two consecutive ion-exchange chromatographic steps on DEAE-Sephadex A-50 columns. The enzyme was purified 13.8-fold and was homogeneous by analytical PAGE and SDS-PAGE. It has a high apparent Mr, of about 100OOO. The pH and temperature optima for its activity were 4.8 and 65 "C respectively. The Km of the purified enzyme for CMC (sodium salt) was 3 mg ml-l. The enzyme displayed low activity toward salicin and p-nitrophenyl P-D-glucoside.The activity was enhanced in the presence of Na+, K+ and Ca2+ but effectively inhibited by Hg2+, Fe2+, Mg2+, Cu2+ and NHZ. Inhibition studies indicated that the enzyme may be a metalloprotein and/or that it requires metal ions for its optimum activity.

Purification and characterization of a low molecular weight xylanase from solid-state cultures of Aspergillus fumigatus Fresenius

“…However, its apparent size by gel filtration was 8.5 kDa, indicating a physical interaction between the enzyme and chromatography resin (result not shown). This is in agreement with the results obtained for xylan-degrading enzymes from T. harzianum, T. reesei, A. oryzae, A. fumigatus VTT-D-71002 and Bacillus sp (1,8,26). A small amount of carbohydrate was found when the purified xylanase II from A. fumigatus Fresenius was assayed with the phenol-sulfuric acid method (9).…”

Alkaliphiles

“…After the demonstration that alkali-treated woodpulp could be biologically bleached by xylanases instead of by the usual environmentally-damaging chemical process using chlorine, the search for thermostable alkaline xylanases has been extensive. Dey 61) isolated an alkaliphilic thermophilic Bacillus sp. (NCIM 59) that produced two types of cellulase-free xylanase at pH 10 and 50˚C.…”

Xylanases of Microorganisms

“…ßê áóëî âñòàíîâëåíî [36], äåøåâ³ гåì³öåëþëîçí³ ñóáñòðàòè, òàê³ ÿê êóêóðóäçÿí³ êà÷àíè, ïøåíè÷í³ ³ ðèñîâ³ âèñ³âêè, ðèñîâà ñîëîìà, êóêóðóäçÿí³ ñòåáëà º íàéá³ëüø ïðèäàòíèìè äëÿ óòâîðåííÿ êñèëàíàç òàêèìè ì³êðîîðгàí³çìàìè ÿê Aspergillus awamori, Penicillium purpurogenum [28], Bacillus sp. MCIB 59 [16]. Нàéá³ëüø ïîâíî îõàðàêòåðèçîâàíî êñèëàíàçè Aspergillus fumigatus і Trichоderma reesei [3], ïðè÷îìó îñòàííÿ ïðîÿâëÿº ìàêñèìàëüíó ñåðåä гðèá³â àêòèâí³ñòü (3350 ÌΕìë -1 ) [26,36].…”

“…[16] ³ гðèáè [23] ïðîäóêóþòü êñèëàíàçè, â³ëüí³ â³ä öåëþëàç. Çäàòí³ñòü ïðîäóêóâàòè êñèëàíàçó ïðè фåðìåíòàö³¿ íà òâåðäèõ ñåðåäîâèùàõ ïîêàçàíà…”

“…[38], àëêàë³ф³ëüíèé, òåðìîф³ëüíèé øòàì Bacillus sp. [16] º гë³êîïðîòå¿íàìè. Âóгëåâîäí³ гðóïè êîâàëåíòíî ïðèºäíàí³ äî á³ëêà àáî ïðèñóòí³ ó âèгëÿä³ êîìïëåêñ³â, çäàòíèõ äî äèñîö³àö³¿.…”