Abstract
식물체 구성성분의 하나인 hemicellulose의 대부분을 차지하는 xylan은 농산 폐기물 또는 목재 성분의 약 30%를 차지하는 풍부한 자원물질이다. 이러한 xylan을 효과적으로 분해하기 위해 Bacillus에서 발현시킨 재조합 endoxylanase를 이용하여 기능성 식품소채인 xylooligosaccharide의 최적 생산 조건을 조사하였다. B. subtilis 재조합 균주 DB431/pJHKJ4를 이용한 발효조 회분배양 결과, endoxylanse의 총 활성은 857 unit/ml이며, 대부분이 세포밖으로 분비됨을 알 수 있었고, 분비효율은 92%로 나타났다. 재조합 endoxylanase를 이용하여 xylan으로부터 xylooligosaccharide 생성을 위한 최적 반응조건을 검토한 결과, xylooligosaccharide 생산을 위한 기질로는 birchwood xylan이 적합함을 알 수 있었고, 4%의 xylan 농도에서 가장 많은 xylooligosaccharide 을 생산하며, xylobiose와 xylotriose가 주생성물임을 알았다. 효소의 농토와 반응시간의 영향은 10 unit의 endoxylanase를 첨가하여 1시간 반응시켰을 때 가장 많은 양의 xylooligosaccharide을 생산할 수 있었고, 반응온도는 <TEX>$40^{\circ}C{\sim}50^{\circ}C$</TEX>가 적합함을 알았다. 결론적으로 재조합 endoxylanase을 이용한 xylooligosaccharide생성에는 10 unit endoxylanase과 4% birchwood xylan을 기질로 이용하여 <TEX>$50^{\circ}C$</TEX>에서 1시간 반응시키는 것이 최적반응 조건임을 알았다. Xylan is a major hemicellulose component of the cell walls of monocots and hardwood, representing up to 30% of the dry weight of these plants. To efficiently hydrolyze xylan, the endoxylanase gene from Bacillus sp. was expressed in B. subtilis DB431 by introducing the plasmid pJHKJ4. The total activity of the recombinant endoxylanase reached about 857 unit/ml by batch fermentation of B. subtilis DB431/pJHKJ4 in LB maltose medium. The majority (>92%) of endoxylanase was efficiently secreted into the culture medium. The recombinant endoxylanase hydrolyzed more the birchwood xylan efficiently than the other xylans. When 4 % concentration of xylan was used, the highest production of xylooligosaccharide was observed, and xylobiose and xylotriose were the major products. Optimal amount of enzyme and reaction time for producing xylooligosaccharide were found to be 10 unit and 1 hr, respectively. In addition, the temperature of <TEX>$40^{\circ}C{\sim}50^{\circ}C$</TEX> gave the highest production of xylooligosaccharide. Consequently, the optimized conditions for the production of xylooligosaccharide through the hydrolysis of xylan were determined as follows: 10 unit endoxylanase, <TEX>$50^{\circ}C$</TEX>, 4% birchwood xylan, 1 hr reaction.
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