Waste biomass coming from a local coffee company, which supplied burnt ground coffee after an incorrect roasting process, was employed as a starting material in the composting plant of the Experimental Station of the University of Naples Federico II at Castel Volturno (CE). The direct molecular characterization of compost using ¹³C-NMR spectra, which was acquired through cross-polarization magic-angle spinning, showed a hydrophobicity index of 2.7% and an alkyl/hydroxyalkyl index of 0.7%. Compost samples that were collected during the early “active thermophilic phase” (when the composting temperature was 63 °C) were analyzed for the prokaryotic community composition and activities. Two complementary approaches, i.e., genomic and predictive metabolic analysis of the 16S rRNA V3–V4 amplicon and culture-dependent analysis, were combined to identify the main microbial factors that characterized the composting process. The whole microbial community was dominated by Firmicutes. The predictive analysis of the metabolic functionality of the community highlighted the potential degradation of peptidoglycan and the ability of metal chelation, with both functions being extremely useful for the revitalization and fertilization of agricultural soils. Finally, three biotechnologically relevant Firmicutes members, i.e., Geobacillus thermodenitrificans subsp. calidus, Aeribacillus pallidus, and Ureibacillus terrenus (strains CAF1, CAF2, and CAF5, respectively) were isolated from the “active thermophilic phase” of the coffee composting. All strains were thermophiles growing at the optimal temperature of 60 °C. Our findings contribute to the current knowledge on thermophilic composting microbiology and valorize burnt ground coffee as waste material with biotechnological potentialities.

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堆肥嗜热阶段的原核生物多样性：以磨碎的咖啡堆肥为例

来自当地咖啡公司的废物生物质，在经过错误的烘焙过程后提供了磨碎的咖啡，被用作那不勒斯费德里科二世大学卡斯特尔沃尔图诺（CE）实验站堆肥厂的原料。使用¹³的堆肥的直接分子表征通过交叉极化魔角纺丝获得的13 C-NMR谱显示疏水指数为2.7％，烷基/羟烷基指数为0.7％。分析了在“活跃的嗜热阶段”早期（堆肥温度为63°C时）收集的堆肥样品的原核生物群落组成和活性。结合了两种互补的方法，即对16S rRNA V3-V4扩增子进行基因组和预测代谢分析以及依赖于培养的分析，以鉴定表征堆肥过程的主要微生物因子。整个微生物群落被Firmicutes所控制。对社区代谢功能的预测分析强调了肽聚糖的潜在降解和金属螯合的能力，这两种功能对于农业土壤的振兴和施肥都非常有用。最后，三个生物技术相关的Firmicutes成员，即地热芽孢杆菌亚种。从咖啡堆肥的“活性嗜热相”中分离出了calidus，Alidbacillus pallidus和Terrenus Tererius（分别为CAF1，CAF2和CAF5菌株）。所有菌株都是在最佳温度60°C下生长的嗜热菌。我们的发现有助于了解当前有关嗜热堆肥微生物学的知识，并以具有生物技术潜力的废料作为原料，对烧成的咖啡进行增值。