Background: Acid Blue 113 (AB113) is a typical azo dye, and the resulting wastewater is toxic and difficult to remove. Methods: The experimental culture was set up for the biodegradation of the azo dye AB113, and the cell growth and dye decolorization were monitored. Transcriptome sequencing was performed in the presence and absence of AB113 treatment. The key pathways and enzymes involved in AB113 degradation were found through pathway analysis and enrichment software (GO, EggNog and KEGG). Results: S. melonis B-2 achieved more than 80% decolorization within 24 h (50 and 100 mg/L dye). There was a positive relationship between cell growth and the azo dye degradation rate. The expression level of enzymes involved in benzoate and naphthalene degradation pathways (NADH quinone oxidoreductase, N-acetyltransferase and aromatic ring-hydroxylating dioxygenase) increased significantly after the treatment of AB113. Conclusions: Benzoate and naphthalene degradation pathways were the key pathways for AB113 degradation. NADH quinone oxidoreductase, N-acetyltransferase, aromatic ring-hydroxylating dioxygenase and CYP450 were the key enzymes for AB113 degradation. This study provides evidence for the process of AB113 biodegradation at the molecular and biochemical level that will be useful in monitoring the dye wastewater treatment process at the full-scale treatment.

Effects of bioaugmentation of the composite microbial culture CES-1 on a full scale textile dye wastewater treatment process were investigated in terms of water quality, sludge reduction, dynamics of microbial community structures and their functional genes responsible for degradation of azo dye, and other chemicals. The removal efficiencies for Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), Suspended Solids (SS), and color intensity (96.4%, 78.4, 83.1, 84.4, and 92.0, respectively) 300–531 days after the augmentation were generally improved after bioaugmentation. The denitrification linked to T-N removal appeared to contribute to the concomitant COD removal that triggered a reduction of sludge (up to 22%) in the same period of augmentation. Azo dye and aromatic compound degradation and other downstream pathways were highly metabolically interrelated. Augmentation of CES-1 increased microbial diversity in the later stages of augmentation when a strong microbial community selection of Acinetobacterparvus, Acinetobacterjohnsonii, Marinobacter manganoxydans, Verminephrobacter sp., and Arcobacter sp. occurred. Herein, there might be a possibility that the CES-1 augmentation could facilitate the indigenous microbial community successions so that the selected communities made the augmentation successful. The metagenomic analysis turned out to be a reasonable and powerful tool to provide with new insights and useful biomarkers for the complex environmental conditions, such as the full scale dye wastewater treatment system undergoing bioaugmentation.

Spent coffee grounds (SCGs), one of the world’s most discarded wastes, may be an excellent resource as an organic fertilizer because of its richness in nutrients. The objective of this study was to develop a quality functional compost using SCGs, rice bran, biochar, SCG extract, and functional microbes (plant growth promoting and plant pathogen-suppression bacteria), and then to test their functional efficacy for a potential commercial application. Essentially, two types of representative composts (Tr_1 and Tr_5 on the laboratory and pilot scale, respectively) were developed and passed all the official commercial quality standards. For pilot-scale composting, populations of Halotalea_uc, Corynebacterium nuruki, and Lactobacillus acidipiscis increased by augmentation of the composting microbes (MA-1) and the functional microbes (Bacillus cereus SB-3, Bacillus toyonensis SB-4, and Streptomyces sasae St-3). The higher total flavonoid content (11% increase compared to control) of pepper leaves in PT-1 and the higher TEAC in PT-1 (36.2%) and PT-2 (32.5%) proved the efficacy of the functional composts bioaugmented with the functional microbes. The seedling growth of radish seeds treated with Streptomyces sasae St-3 as a biocontrol agent significantly increased despite the presence of the pathogen Fusarium oxysporum f. sp. lactucae. The total phenol content and TEAC in pepper plant leaves were significantly higher in Tr_5 than in the control (Tr_4), whereas there were no differences in Tr_4 and Tr_5 infested with the fungal pathogens, indicating that SB-3, SB-4, and St-3 cultures amended within the compost (Tr_5) may facilitate the production of the antioxidants in the absence of the pathogens. However, a significant reduction in the antioxidants (total phenolic content and TEAC) was observed in the pepper plants whose roots were infected with the pathogens, indicating that the pathogens could neutralize functionalities of the functional microbes. It was concluded that the enhancement of functional microbes in the compost would aid in the biological control of pathogens in the soil environment. Further functional compost studies are necessary in terms of mechanisms of plant growth-promotion, mechanisms of pathogen suppression by the actinobacterial biocontrol agents, and interactions between the two mechanisms, as well as quality enhancement of the composts.