Faculty of Natural Sciences, Universidad Icesi, Calle 18 No 122-135, Cali, Colombia.
Appl Microbiol Biotechnol. 2019 Jul;103(13):5401-5410. doi: 10.1007/s00253-019-09859-z. Epub 2019 May 7.
Cyanide is toxic to most living organisms. The toxicity of cyanide derives from its ability to inhibit the enzyme cytochrome C oxidase of the electronic transport chain. Despite its high toxicity, several industrial processes rely on the use of cyanide, and considerable amounts of industrial waste must be adequately treated before discharge. Biological treatments for the decontamination of cyanide waste include the use of microorganisms and enzymes. Regarding the use of enzymes, cyanide dihydratase (CynD), which catalyzes the conversion of cyanide into ammonia and formate, is an attractive candidate. Nevertheless, the main impediment to the effective use of this enzyme for the biodegradation of cyanide is the marked intolerance to the alkaline pH at which cyanide waste is kept. In this work, we explore the operational capabilities of whole E. coli cells overexpressing Bacillus pumilus CynD immobilized in three organic polymer matrices: chitosan, polyacrylamide, and agar. Remarkably, the immobilized cells on agar and polyacrylamide retained more than 80% activity even at pH 10 and displayed high reusability. Conversely, the cells immobilized on chitosan were not active. Finally, the suitability of the active complexes for the degradation of free cyanide from a solution derived from the gold processing industry was demonstrated.
氰化物对大多数生物都具有毒性。氰化物的毒性源自其抑制电子传递链细胞色素 C 氧化酶的能力。尽管氰化物毒性很高，但仍有几个工业过程依赖于氰化物的使用，并且在排放之前必须对相当数量的工业废物进行充分处理。用于氰化物废物脱除的生物处理方法包括使用微生物和酶。关于酶的使用，氰化物双加氧酶（CynD）是一种有吸引力的候选酶，它可以催化氰化物转化为氨和甲酸盐。然而，该酶用于氰化物生物降解的主要障碍是对氰化物废物保持的碱性 pH 值的明显耐受性。在这项工作中，我们研究了在三种有机聚合物基质（壳聚糖、聚丙烯酰胺和琼脂）中固定化巴氏芽孢杆菌 CynD 过表达的整个大肠杆菌细胞的操作能力。值得注意的是，固定在琼脂和聚丙烯酰胺上的细胞即使在 pH 值为 10 时仍保持超过 80%的活性，并且具有很高的可重复使用性。相反，固定在壳聚糖上的细胞没有活性。最后，证明了活性复合物适用于从金矿加工行业衍生的溶液中降解游离氰化物。
