## 4 Conclusions  
BSG and SCG solid sidestreams at the point of generation have low bacterial loads (3.53 \(\pm\) 0.03 and \(<\)1 log\({}_{10}\) CFU/g) while lacking a distinct microbiome and are suitable for valorization into food, feed, cosmetics, or other applications. However, these solid sidestreams undergo rapid chemical and biological changes during logistics, and after collection by recycling companies, they have high bacterial loads (\(>\)6 log\({}_{10}\) CFU/g) and a distinct microbiome, dominated by _Bacillus_ for BSG and LAB for SCG, arising from environmental contamination. This highlights the significant risk of contamination with food-borne contaminants such as _B. cereus_, although it was not identified in this study. The microbiome changed significantly during storage under industrially relevant aerobic and anaerobic conditions. Rapid bacterial growth occurred, stabilizing around day 3 for BSG and day 7 for SCG, with over 100-fold increases in bacterial loads (\(>\)8 log\({}_{10}\) CFU/g) by day 14 under aerobic conditions. _B. coagul_s (reclassified as _Heyndrickxia coagul_s) was identified as the most prevalent bacterial species in BSG on storage and was also found in SCG. Extensive fungal growth (\(>\)7 log\({}_{10}\) CFU/g) was observed for BSG, with potential aflatoxin-producing _A. flavus_ being the dominant species, which was also identified in SCG stored aerobically. Aflatoxin contamination is a major food and feed safety concern and must be managed if BSG and SCG are valorized for such applications. Anaerobic storage inhibited fungal growth and led to changes in the bacterial microbiome. A dynamic of LAB and AAB co-dependency was identified, likely under microaerobic conditions, while facultative anaerbes such as _Pseudomonas_, _Enterococcus_, and _Enterobacter_, and even obligate anaerobic _Clostridia_, were also identified in anaerobic conditions. These findings highlight critical food safety concerns while providing essential information for establishing shelf-life and storage guidelines for BSG and SCG, with the aim of promoting the further valorization of these solid sidestreams in industrialized Asia. The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app14219759/s1](https://www.mdpi.com/article/10.3390/app14219759/s1)]([https://www.mdpi.com/article/10.3390/app14219759/s1](https://www.mdpi.com/article/10.3390/app14219759/s1)): Figure S1: Experimental setup used for storage trials. Figures S2-S5: Physical measurements of temperature and humidity by dataloggers for each try and drum containing BSG; Figures S6-S9: Physical measurements of temperature and humidity by dataloggers for each try and drum containing SCG. Figure S10: Quantitative polymerase chain reaction (qPCR) of BSG and SCG during 14 days of storage in trays (BSG-2 and SCG-2) and drums (BSG-2 and SCG-3). Figure S11: Taxonomic abundance cluster heatmap hierarchical clustering of samples for the top 35 bacterial species of BSG-1, BSG-2, and BSG-3 as received and after 14 days of storage in trays (BSG-2) and drums (BSG-2). Figure S12: Taxonomic abundance cluster heatmap hierarchical clustering of samples for the top 35 bacterial species of SCG-2 and SCG-3 as received and after 14 days of storage in trays (SCG-2) and drums (SCG-3). Table S1: PCR primers and run conditions for qPCR of BSG and SCG samples. References [17; 65] are cited in the Supplementary Materials. Conceptualization, C.H. and E.C.P. ; Formal analysis, Q.K.C., S.H. and F.N. ; Funding Acquisition, M.W. ; Investigation, Q.K.C. and S.H. ; Methodology, Q.K.C. and S.H. ; Project Administration, M.W. ; Supervision, C.H., M.W. and E.C.P. ; Visualization, C.H. ; Writing--OriginalDraft, C.H. ; Writing--Review and Editing, M.W. and E.C.P. All authors have read and agreed to the published version of the manuscript.