Fingerprint of Exhaust Gases and Database of Microbial Diversity During Silkworm Excrement Composting

Composting can convert silkworm excrement (SE) into good fertilizer, but the popularization of this practice is greatly hampered due to the strong odor produced. Determining the gas pollutants, the potential native aerogenic microorganisms and deodorant microorganism communities will lay foundations for developing good strategies to deal with malodor pollution from SE composting. This study qualitatively and quantitatively analyzed the exhaust gas and the microbial diversity. With a combination of solid-phase micro-extraction-gas chromatography tandem mass spectrometry technology and other methods of Chinese national standards, 43 odor pollutants from SE composting were identified and quantified. Ammonia, sulfur dioxide and hydrogen sulfide were the three major pollutants among the volatile inorganic compounds, with concentrations far exceeding the permissible standards for workplaces in China. 5-Ethyl-2,2,3-trimethyl-heptane, 2,2,4,6,6-5-methyl-heptane and 5-isobutyl-nonane accounted for 46.58% of volatile organic compounds. Using analysis of ribosome DNA sequences with Illumina Miseq PE 2 * 250, a next generation high-throughput sequencing technology, more than 694 bacteria (and actinomycetes) and more than 136 fungi were annotated, including groups of native aerogenic microorganisms and deodorant microorganisms. This study indicated a serious malodor problem and abundant microorganisms from SE composting and provided basic data not only for odor pollution control but also for future functional microorganism studies.

堆肥化可将蚕沙（silkworm excrement, SE）转化为优质肥料，但该工艺的推广却因产生的强烈恶臭而受到极大阻碍。明确气体污染物、潜在土著产气微生物及除臭微生物群落，可为制定蚕沙堆肥恶臭污染防控的有效策略奠定基础。本研究对堆肥废气与微生物多样性进行了定性与定量分析。采用固相微萃取-气相色谱串联质谱（solid-phase micro-extraction-gas chromatography tandem mass spectrometry）技术结合多项中国国家标准方法，共鉴定并定量了蚕沙堆肥产生的43种恶臭污染物。挥发性无机物中的主要污染物为氨、二氧化硫与硫化氢，其浓度远高于我国工作场所的限值标准。5-乙基-2,2,3-三甲基庚烷、2,2,4,6,6-5-甲基庚烷与5-异丁基壬烷约占挥发性有机物总量的46.58%。依托下一代高通量测序技术Illumina Miseq PE 2×250开展核糖体DNA序列分析，共注释得到694种及以上细菌（含放线菌）与136种及以上真菌，其中涵盖土著产气微生物与除臭微生物类群。本研究证实蚕沙堆肥存在严重的恶臭问题且微生物资源丰富，不仅为恶臭污染防控提供了基础数据，也为后续功能微生物研究奠定了支撑。