Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität (WWU) Muenster, Corrensstraße 3, 48149 Münster, Germany.
Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität (WWU) Muenster, Schlossplatz 8, 48143 Münster, Germany.
FEMS Microbiol Lett. 2019 Jan 1;366(1). doi: 10.1093/femsle/fny294.
Defined organic waste products are ideal and sustainable secondary feedstocks for production organisms in microbial biotechnology. Chitin from mycelia of fungal fermentation processes represents a homogeneous and constantly available waste product that can, however, not be utilised by typical bacterial production strains. Therefore, enzymes that degrade chitin within fungal mycelia have to be identified and expressed in production organisms. In this study, chitin-degrading bacteria were enriched and isolated from lake water with mycelia of Aspergillus tubingensis as sole organic growth substrate. This approach yielded solely strains of Aeromonas hydrophila. Comparison of the isolated strains with other A. hydrophila strains regarding their chitinolytic activities on fungal mycelia identified strain AH-1N as the best enzyme producer. From this strain, a chitinase (EC:3.2.1.14) was identified by peptide mass fingerprinting. Heterologous expression of the respective gene combined with mass spectrometry showed that the purified enzyme was capable of releasing chitobiose from fungal mycelia with a higher yield than a well-described chitinase from Serratia marcescens. Expression of the newly identified chitinase in biotechnological production strains could be the first step for making fungal mycelium accessible as a secondary feedstock. Additionally, the enrichment strategy proved to be feasible for identifying strains able to degrade fungal chitin.
定义明确的有机废物是微生物生物技术中生产生物的理想和可持续的二次原料。真菌发酵过程中的菌丝体甲壳素是一种均匀且不断可用的废物，但不能被典型的细菌生产菌株利用。因此，必须鉴定和表达能够降解真菌菌丝体中甲壳素的酶。在这项研究中，从仅含有 Aspergillus tubingensis 菌丝体作为唯一有机生长基质的湖水 中富集和分离了能够降解甲壳素的细菌。这种方法仅产生了嗜水气单胞菌（Aeromonas hydrophila）的菌株。将分离的菌株与其他嗜水气单胞菌菌株的真菌菌丝体的甲壳素酶活性进行比较，确定了菌株 AH-1N 是最好的产酶菌株。从该菌株中，通过肽质量指纹图谱鉴定出一种几丁质酶（EC：3.2.1.14）。该基因的异源表达结合质谱分析表明，与来自粘质沙雷氏菌的一种描述良好的几丁质酶相比，该酶能够从真菌菌丝体中释放出更高产量的壳二糖。在生物技术生产菌株中表达新鉴定的几丁质酶可能是使真菌菌丝体作为二次原料可利用的第一步。此外，富集策略被证明是可行的，可用于鉴定能够降解真菌甲壳素的菌株。
