INRAE, Univ. Montpellier, LBE, 102 Avenue des étangs, 11100 Narbonne, France.
Department of Thematic Studies-Environmental Change and Biogas Research Center, Linköping University, 581 83 Linköping, Sweden.
Sci Total Environ. 2023 Jun 15;877:162882. doi: 10.1016/j.scitotenv.2023.162882. Epub 2023 Mar 17.
The recalcitrant structures either from substrate or microbial biomass contained in digestates after anaerobic digestion (AD) highly influence digestate valorization. To properly assess the microbial biomass contribution to the digested organic matter (OM), a combination of characterization methods and the use of various substrate types in anaerobic continuous reactors was required. The use of totally biodegradable substrates allowed detecting soluble microbial products via fluorescence spectroscopy at emission wavelengths of 420 and 460 nm while the protein-like signature was enhanced by the whey protein. During reactors' operation, a transfer of complex compounds to the dissolved OM from the particulate OM was observed through fluorescence applied on biochemical fractionation. Consequently, the fluorescence complexity index of the dissolved OM increased from 0.59-0.60 to 1.06-1.07, whereas it decreased inversely for the extractable soluble from the particulate OM from 1.16-1.19 to 0.42-0.54. Accordingly, fluorescence regional integration showed differences among reactors based on visual inspection and orthogonal partial latent structures (OPLS) analysis. Similarly, the impact of the substrate type and operation time on the particulate OM was revealed by C nuclear magnetic resonance using OPLS, providing a good model (RX = 0.93 and Q = 0.8) with a clear time-trend. A high signal resonated at ∼30 ppm attributed to CH-groups in the aliphatic chain of lipid-like structure besides carbohydrates intensities at 60-110 ppm distinguished the reactor fed with whey protein from the other, which was mostly biomass related. Indeed, this latter displayed a higher presence of peptidoglycan (δH/C: 1.6-2.0/20-25 ppm) derived from microbial biomass by H-C heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance. Interestingly, the sample distribution obtained by non-metric multidimensional scaling of bacterial communities resembled the attained using C NMR properties, opening new research perspectives. Overall, this study discloses the microbial biomass contribution to digestates composition to improve the OM transformation mechanism knowledge.
厌氧消化（AD）后消化物中顽固的结构，无论是来自基质还是微生物生物质，都会强烈影响消化物的增值。为了正确评估微生物生物质对消化有机物质（OM）的贡献，需要结合各种特征描述方法和在厌氧连续反应器中使用各种基质类型。使用完全可生物降解的基质可以通过荧光光谱在 420nm 和 460nm 的发射波长下检测到可溶微生物产物，而乳清蛋白则增强了蛋白质样特征。在反应器运行过程中，通过荧光应用于生化分级，观察到从颗粒 OM 向溶解 OM 转移复杂化合物。因此，溶解 OM 的荧光复杂性指数从 0.59-0.60 增加到 1.06-1.07，而从颗粒 OM 中可提取的可溶性 OM 则相反，从 1.16-1.19 减少到 0.42-0.54。因此，荧光区域积分根据视觉检查和正交偏最小二乘（OPLS）分析在反应器之间存在差异。同样，基于 OPLS 的 C 核磁共振也揭示了基质类型和运行时间对颗粒 OM 的影响，提供了一个很好的模型（RX=0.93，Q=0.8），具有明显的时间趋势。在 ∼30ppm 处出现的高信号归因于脂质样结构中 CH 基团的脂肪链，除了 60-110ppm 处的碳水化合物强度外，还区分了用乳清蛋白喂养的反应器与其他反应器，后者主要与生物质有关。事实上，后者显示出更高的微生物生物质来源的肽聚糖（δH/C：1.6-2.0/20-25ppm）存在，通过 H-C 异核单量子相干（HSQC）核磁共振。有趣的是，通过细菌群落的非度量多维标度分析得到的样品分布与通过 C NMR 特性获得的分布相似，为新的研究提供了新的视角。总的来说，这项研究揭示了微生物生物质对消化物成分的贡献，以提高对 OM 转化机制的认识。
