美國(guó)能源部國(guó)家可再生能源實(shí)驗(yàn)室與生物能源科學(xué)中心的科學(xué)家通過(guò)將不同的顯微成像技術(shù)相結(jié)合,，深入研究生物質(zhì)細(xì)胞壁結(jié)構(gòu)與酶解之間的關(guān)系,，這些發(fā)現(xiàn)將會(huì)提高糖的產(chǎn)量，降低生物燃料成本,。研究成果發(fā)表在“科學(xué)”雜志上,，題目為：“How Does Plant Cell Wall Nanoscale Architecture Correlate with Enzymatic Digestibility?”
首席科學(xué)家Ding SY教授說(shuō)：新的成像技術(shù)使科學(xué)家可以查看從毫米到納米級(jí)的植物結(jié)構(gòu)，這樣不僅可以研究植物細(xì)胞壁的結(jié)構(gòu),，同時(shí)也可以研究負(fù)責(zé)降解細(xì)胞壁聚合物的酶及這些酶對(duì)細(xì)胞壁的作用方式,。了解生物質(zhì)結(jié)構(gòu)的傳統(tǒng)方法是化學(xué)法，通過(guò)破壞各個(gè)組成部分以進(jìn)行分析,，這種分析方法將失去結(jié)構(gòu)的完整性,。
成像技術(shù)使科學(xué)家更詳細(xì)深入的了解細(xì)胞壁結(jié)構(gòu)和酶解細(xì)胞壁碳水化合物聚合物以釋放單糖的過(guò)程,。科研團(tuán)隊(duì)還利用成像技術(shù)研究了除去木質(zhì)素對(duì)生物質(zhì)的水解的影響、細(xì)胞壁結(jié)構(gòu)的納米尺度的變化,，及這些變化對(duì)反應(yīng)速率的影響,。
NREL的研究小組研究了真菌和細(xì)菌的酶系統(tǒng),，這兩種系統(tǒng)都在生物燃料工業(yè)中作為生物催化劑生產(chǎn)糖中間體,。對(duì)細(xì)菌中的酶研究表明，不同的酶通過(guò)一個(gè)大型的腳手架蛋白結(jié)合成多酶復(fù)合體作用于細(xì)胞壁,，而真菌的酶系統(tǒng)更傾向于單獨(dú)作戰(zhàn),，雖然最終的結(jié)果是由多種酶作用共同產(chǎn)生。研究人員還發(fā)現(xiàn),，酶越容易接近細(xì)胞壁,，對(duì)細(xì)胞壁的降解速率則越高。
文章最后的結(jié)論認(rèn)為：理想的預(yù)處理材料應(yīng)該是細(xì)胞壁已經(jīng)除去木質(zhì)素，并細(xì)胞壁內(nèi)部附著完整的結(jié)構(gòu)多糖的材料,，這是一種相對(duì)松散,、多孔原生狀結(jié)構(gòu)，利于酶的進(jìn)入及講解,。而非出去細(xì)胞壁中的海綿狀碳水化合物,，從而是剩余的部分坍塌更為緊密的結(jié)構(gòu)。 (生物谷Bioon.com)
DOI: 10.1126/science.1227491
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How Does Plant Cell Wall Nanoscale Architecture Correlate with Enzymatic Digestibility?
Shi-You Ding1,*,†, Yu-San Liu1,*, Yining Zeng1, Michael E. Himmel1, John O. Baker1, Edward A. Bayer2
Greater understanding of the mechanisms contributing to chemical and enzymatic solubilization of plant cell walls is critical for enabling cost-effective industrial conversion of cellulosic biomass to biofuels. Here, we report the use of correlative imaging in real time to assess the impact of pretreatment, as well as the resulting nanometer-scale changes in cell wall structure, upon subsequent digestion by two commercially relevant cellulase systems. We demonstrate that the small, noncomplexed fungal cellulases deconstruct cell walls using mechanisms that differ considerably from those of the larger, multienzyme complexes (cellulosomes). Furthermore, high-resolution measurement of the microfibrillar architecture of cell walls suggests that digestion is primarily facilitated by enabling enzyme access to the hydrophobic cellulose face. The data support the conclusion that ideal pretreatments should maximize lignin removal and minimize polysaccharide modification, thereby retaining the essentially native microfibrillar structure.
