Casciello Carmine, Tonin Fabio, Berini Francesca, Fasoli Elisa, Marinelli Flavia, Pollegioni Loredano, Rosini Elena
Department of Biotechnology and Life Sciences, University of Insubria, via J.H. Dunant 3, 21100 Varese, Italy; The Protein Factory Research Center, Politecnico of Milano and University of Insubria, via Mancinelli 7, 20131 Milano, Italy.
Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico of Milano, via Mancinelli 7, 20131, Milano, Italy.
Biotechnol Rep (Amst). 2017 Jan 3;13:49-57. doi: 10.1016/j.btre.2016.12.005. eCollection 2017 Mar.
Degradation of lignin constitutes a key step in processing biomass to become useful monomers but it remains challenging. Compared to fungi, bacteria are much less characterized with respect to their lignin metabolism, although it is reported that many soil bacteria, especially actinomycetes, attack and solubilize lignin. In this work, we screened 43 filamentous actinomycetes by assaying their activity on chemically different substrates including a soluble and semi-degraded lignin derivative (known as alkali lignin or Kraft lignin), and we discovered a novel and valuable peroxidase activity produced by the recently classified actinomycete Compared to known fungal manganese and versatile peroxidases, the stability of peroxidase activity at alkaline pHs and its thermostability are significantly higher. From a kinetic point of view, peroxidase activity shows a for HO similar to that of and enzymes and a lower affinity for Mn, whereas it differs from the six manganese peroxidase isoenzymes described in the literature. Additionally, peroxidase shows a remarkable dye-decolorizing activity that expands its substrate range and paves the way for an industrial use of this enzyme. These results confirm that by exploring new bacterial diversity, we may be able to discover and exploit alternative biological tools putatively involved in lignin modification and degradation.
木质素的降解是将生物质加工成有用单体的关键步骤，但仍然具有挑战性。与真菌相比，细菌在木质素代谢方面的特征要少得多，尽管据报道许多土壤细菌，尤其是放线菌，能够攻击并溶解木质素。在这项工作中，我们通过检测43种丝状放线菌对化学性质不同的底物（包括一种可溶的、半降解的木质素衍生物，即碱木质素或硫酸盐木质素）的活性进行了筛选，并且我们发现了一种由最近分类的放线菌产生的新型且有价值的过氧化物酶活性。与已知的真菌锰过氧化物酶和多功能过氧化物酶相比，该过氧化物酶活性在碱性pH值下的稳定性及其热稳定性显著更高。从动力学角度来看，该过氧化物酶活性对H₂O₂的表现类似于其他酶，对Mn²⁺的亲和力较低，而这与文献中描述的六种锰过氧化物酶同工酶不同。此外，该过氧化物酶表现出显著的染料脱色活性，扩大了其底物范围，并为该酶的工业应用铺平了道路。这些结果证实，通过探索新的细菌多样性，我们或许能够发现并利用可能参与木质素修饰和降解的替代生物工具。
