Horizon 1 1 17 ACLN : Articles dans des revues avec comité de lecture non répertoriées par l'AERES Environmental Science and Pollution Research 16725-16739 FRANCE 2024 fdi:010095706 ENG Environmental Science and Pollution Research 1614-7499 28 10.1007/s11356-024-33629-8 https://www.documentation.ird.fr/hor/fdi:010095706 https://www.documentation.ird.fr/intranet/publi/2025-11/010095706.pdf 32 Horizon (IRD) Fermented forest litter (FFL) is a bioproduct used as biofertilizer for several decades in Eastern Asia and Latin America. It is locally handcrafted by farmers in anaerobic conditions by fermenting forest litter added with agricultural by-products such as whey, cereal bran, and molasses. The aim of this study was to characterize the FFL process and product through gas and liquid chromatography analyses. It also provides some highlights on the influence of O 2 on this solid-state culture. Under anoxic condition, a maximum CO 2 production rate (CDPR) of 0.41 mL/h?g dry matter (dm) was reached after 8 days. The main volatile organic compounds (VOCs) were ethanol and ethyl acetate, with a production rate profile similar to CDPR. After 21 days of culture, no residual sucrose nor lactose was detected. Lactic and acetic acids reached 58.8 mg/g dm and 10.2 mg/g dm, respectively, ensuring the acidification of the matrix to a final pH of 4.72. A metabarcoding analysis revealed that heterolactic acid bacteria (Lentilactobacillus, Leuconostoc), homolactic acid bacteria (Lactococcus), and yeasts (Sac- charomyces, Clavispora) were predominant. Predicted genes in the microbiome confirmed the potential link between detected bacteria and acids and VOCs produced. When O 2 was fed to the cultures, final pH reached values up to 8.5. No significant amounts of lactic nor acetic acid were found. In addition, a strong shift in microbial communities was observed, with a predominance of Proteobacteria and molds, among which are potential pathogens like Fusarium species. This suggests that particular care must be brought to maintain anoxic conditions throughout the process. 098 ; 084