Covalent immobilization on chitosan of ligninolytic enzymes obtained from Ganoderma parvulum and their application in the biodegradation of acetaminophen

Water quality is essential to maintain human well-being and the balance of ecosystems. A subclass of organic chemicals that are being detected with increasing frequency in water bodies have been classified as emerging pollutants; Among them, pharmaceutical products are under special attention because they have biological activity and some of high consumption, as acetaminophen, are being released in large quantities into the environment causing damage. Due to this, various methods and techniques have been developed and studied to degrade contaminants. Fungi have drawn particular attention, and among them, the most promising and studied are white-rot fungi, thanks to their ligninolytic enzymes. Although free enzymes have applicability, research on immobilized enzymes is of great industrial interest, due to the fact that they can be used for more than one catalytic cycle. Initially, enzyme production was carried out cultivating Ganoderma parvulum in a 5L bioreactor. Subsequently, the enzymes were partially purified and covalently immobilized on chitosan microspheres. It was found that among the parameters evaluated, the best immobilization efficiency was obtained with 10% glutaraldehyde, 60 minutes of crosslinking time and 10,000 U/L of laccase. In addition, the operational stability of the microparticles with enzymes and their application in the biotransformation of emerging contaminants such as acetaminophen were evaluated. Finding up to 98% biosorption/biotransformation of acetaminophen associated with immobilized enzymes after four hours of reaction, results that are sought due to the ubiquitous presence of these drugs in nature and their toxicological properties in the environment.水质对于维持人类福祉与生态系统平衡至关重要。一类在水体中检出频率持续攀升的有机化学物亚类已被划归为新兴污染物；其中，药品因具备生物活性且部分品种消费量极高而受到特别关注，例如对乙酰氨基酚（acetaminophen）正被大量排放至环境并造成损害。鉴于此，各类用于降解污染物的方法与技术已得到开发与研究。真菌已受到广泛关注，其中以白腐真菌（white-rot fungi）最具应用前景且研究最为深入，这得益于其分泌的木质素降解酶。尽管游离酶具备应用潜力，但固定化酶的研究因可多次用于催化循环而具有极高的工业价值。最初，研究通过在5升生物反应器中培养小孢灵芝（Ganoderma parvulum）来实现酶的生产。随后，对酶进行部分纯化，并将其共价固定于壳聚糖微球之上。研究发现，在所评估的参数中，当使用10%戊二醛（glutaraldehyde）、交联时长60分钟以及10000 U/L的漆酶（laccase）时，可获得最佳固定化效率。此外，研究还评估了负载酶的微颗粒的操作稳定性，以及其在对乙酰氨基酚等新兴污染物生物转化中的应用效果。经4小时反应后，固定化酶可实现对乙酰氨基酚高达98%的生物吸附/生物转化效率；鉴于此类药物在自然环境中普遍存在且具有环境毒理学特性，这一结果正是研究期望达成的目标。