Carbohydrate rich substrates such as lignocellulosic hydrolysates remain one of the primary sources of potentially renewable fuel and bulk chemicals. The pentose sugar d-xylose is often present in significant amounts along with hexoses. Saccharomyces cerevisiae can acquire the ability to metabolize d-xylose through expression of heterologous d-xylose isomerase (XI). This enzyme is notoriously difficult to express in S. cerevisiae and only fourteen XIs have been reported to be active so far. We cloned a new d-xylose isomerase derived from microorganisms in the gut of the wood-feeding beetle Odontotaenius disjunctus. Although somewhat homologous to the XI from Piromyces sp. E2, the new gene was identified as bacterial in origin and the host as a Parabacteroides sp. Expression of the new XI in S. cerevisiae resulted in faster aerobic growth than the XI from Piromyces on d-xylose media. The d-xylose isomerization rate conferred by the new XI was also 72% higher, while absolute xylitol production was identical in both strains. Interestingly, increasing concentrations of xylitol (up to 8 g L⁻¹) appeared not to inhibit d-xylose consumption. The newly described XI displayed 2.6 times higher specific activity, 37% lower K_M for d-xylose, and exhibited higher activity over a broader temperature range, retaining 51% of maximal activity at 30 °C compared with only 29% activity for the Piromyces XI.

富含碳水化合物的底物如木质纤维素水解物仍然是潜在可再生燃料和大宗化学品的主要来源之一。戊糖d-木糖通常与己糖一起大量存在。酿酒酵母可以通过表达异源d-木糖异构酶 (XI)获得代谢d-木糖的能力。众所周知，这种酶很难在酿酒酵母中表达，目前只有 14 种 XI 被报道具有活性。我们在食木甲虫Odontotaenius disjunctus的肠道中克隆了一种新的d-木糖异构酶. 虽然与来自Piromyces sp.的 XI 有点同源。E2，新基因被鉴定为起源于细菌，宿主为Parabacteroides sp。新 XI 在酿酒酵母中的表达导致比在d-木糖培养基上来自Piromyces的 XI 更快的有氧生长。新 XI 赋予的d-木糖异构化率也高出 72%，而两种菌株的绝对木糖醇产量相同。有趣的是，增加木糖醇浓度（高达8 g L ^-1）似乎不会抑制d-木糖消耗。新描述的 XI 比活性高 2.6 倍，K _M低 37%对于d木糖，并在更宽的温度范围内显示出较高的活性，只有29为％活性相比在30℃下保持最大活性的51％的单鞭毛XI。