Arizzi M, Morra S, Gilardi G, Pugliese M, Gullino M L, Valetti F
Department of Life Sciences and Systems Biology, University of Torino, Via Accademia Albertina 13, 10123, Torino, Italy.
Acea Engineering Laboratories Research Innovation SpA, Roma, Italy.
Biotechnol Biofuels. 2021 Sep 16;14(1):182. doi: 10.1186/s13068-021-02028-3.
Bio-hydrogen production via dark fermentation of low-value waste is a potent and simple mean of recovering energy, maximising the harvesting of reducing equivalents to produce the cleanest fuel amongst renewables. Following several position papers from companies and public bodies, the hydrogen economy is regaining interest, especially in combination with circular economy and the environmental benefits of short local supply chains, aiming at zero net emission of greenhouse gases (GHG). The biomasses attracting the largest interest are agricultural and urban green wastes (pruning of trees, collected leaves, grass clippings from public parks and boulevards), which are usually employed in compost production, with some concerns over the GHG emission during the process. Here, an alternative application of green wastes, low-value compost and intermediate products (partially composted but unsuitable for completing the process) is studied, pointing at the autochthonous microbial consortium as an already selected source of implementation for biomass degradation and hydrogen production. The biocatalysts investigated as mainly relevant for hydrogen production were the [FeFe]-hydrogenases expressed in Clostridia, given their very high turnover rates.
Bio-hydrogen accumulation was related to the modulation of gene expression of multiple [FeFe]-hydrogenases from two strains (Clostridium beijerinckii AM2 and Clostridium tyrobutyricum AM6) isolated from the same waste. Reverse Transcriptase quantitative PCR (RT-qPCR) was applied over a period of 288 h and the RT-qPCR results showed that C. beijerinckii AM2 prevailed over C. tyrobutyricum AM6 and a high expression modulation of the 6 different [FeFe]-hydrogenase genes of C. beijerinckii in the first 23 h was observed, sustaining cumulative hydrogen production of 0.6 to 1.2 ml H/g VS (volatile solids). These results are promising in terms of hydrogen yields, given that no pre-treatment was applied, and suggested a complex cellular regulation, linking the performance of dark fermentation with key functional genes involved in bio-H production in presence of the autochthonous consortium, with different roles, time, and mode of expression of the involved hydrogenases.
An applicative outcome of the hydrogenases genes quantitative expression analysis can be foreseen in optimising (on the basis of the acquired functional data) hydrogen production from a nutrient-poor green waste and/or low added value compost, in a perspective of circular bioeconomy.
通过对低价值废物进行暗发酵生产生物氢是一种有效且简单的能量回收方式，能最大程度地获取还原当量以生产可再生能源中最清洁的燃料。在公司和公共机构发布了多篇立场文件之后，氢经济重新受到关注，特别是与循环经济以及本地短供应链的环境效益相结合，目标是实现温室气体（GHG）的净零排放。最受关注的生物质是农业和城市绿色废物（树木修剪物、收集的树叶、公园和林荫道的草屑），这些通常用于堆肥生产，但人们对该过程中的温室气体排放有所担忧。在此，研究了绿色废物、低价值堆肥和中间产物（部分堆肥但不适于完成整个堆肥过程）的另一种应用，将本地微生物群落视为已选定的生物质降解和氢气生产的实施来源。由于其极高的周转率，研究中主要与氢气生产相关的生物催化剂是梭菌中表达的[FeFe] -氢化酶。
生物氢的积累与从同一废物中分离出的两种菌株（拜氏梭菌AM2和酪丁酸梭菌AM6）中多种[FeFe] -氢化酶基因表达的调节有关。在288小时内进行了逆转录定量PCR（RT - qPCR），结果表明拜氏梭菌AM2优于酪丁酸梭菌AM6，并且观察到拜氏梭菌的6种不同[FeFe] -氢化酶基因在前23小时内有高表达调节，维持了0.6至1.2毫升氢气/克挥发性固体（VS）的累积产氢量。鉴于未进行预处理，这些结果在氢气产量方面很有前景，并表明存在复杂的细胞调节，将暗发酵性能与本地微生物群落存在时参与生物氢生产的关键功能基因联系起来，所涉及的氢化酶具有不同的作用、时间和表达模式。
从循环生物经济的角度来看，可以预见氢化酶基因定量表达分析的应用成果在于（基于获得的功能数据）优化从营养贫乏的绿色废物和/或低附加值堆肥中生产氢气。
