Wood-feeding termite gut symbionts as an obscure yet promising source of novel manganese peroxidase-producing oleaginous yeasts intended for azo dye decolorization and biodiesel production

• Published in: Biotechnology for biofuels 2021-12, Vol.14 (1), p.229-27, Article 229
• Main Authors: Al-Tohamy, Rania, Sun, Jianzhong, Khalil, Maha A, Kornaros, Michael, Ali, Sameh Samir
• Format: Article
• Language: English
• Subjects: Accumulation; Acetic acid; Agricultural wastes; Azo compounds; Azo dyes; Biodegradation; Biodiesel fuels; Biofuels; Biomass; Chemical properties; Consortia; Decoloring; Decolorization; Degradation; Diesel; Dyes; Feeding; Formic acid; Furfural; Industrial wastewater; Inhibitors; International standards; Lignocellulose; Lignocellulose degradation inhibitors; Lipids; Manganese; Manganese peroxidase; Manganese peroxidases; Methods; Meyerozyma caribbica; Microbial enzymes; Microbiological research; Microbiota (Symbiotic organisms); Oleaginous yeasts; Orange II; Peroxidase; Physicochemical properties; Physiological aspects; Pollutants; Production processes; Refuse and refuse disposal; Renewable energy; Strains (organisms); Substrates; Symbionts; Termites; Vanillin; Waste management; Wastewater; Wood; Wood-feeding termite gut symbionts; Yeast; Yeast fungi; Yeasts
• ISSN: 1754-6834; 1754-6834
• DOI: 10.1186/s13068-021-02080-z

The ability of oxidative enzyme-producing micro-organisms to efficiently valorize organic pollutants is critical in this context. Yeasts are promising enzyme producers with potential applications in waste management, while lipid accumulation offers significant bioenergy production opportunities. The aim of this study was to explore manganese peroxidase-producing oleaginous yeasts inhabiting the guts of wood-feeding termites for azo dye decolorization, tolerating lignocellulose degradation inhibitors, and biodiesel production. Out of 38 yeast isolates screened from wood-feeding termite gut symbionts, nine isolates exhibited high levels of extracellular manganese peroxidase (MnP) activity ranged between 23 and 27 U/mL after 5 days of incubation in an optimal substrate. Of these MnP-producing yeasts, four strains had lipid accumulation greater than 20% (oleaginous nature), with Meyerozyma caribbica SSA1654 having the highest lipid content (47.25%, w/w). In terms of tolerance to lignocellulose degradation inhibitors, the four MnP-producing oleaginous yeast strains could grow in the presence of furfural, 5-hydroxymethyl furfural, acetic acid, vanillin, and formic acid in the tested range. M. caribbica SSA1654 showed the highest tolerance to furfural (1.0 g/L), 5-hydroxymethyl furfural (2.5 g/L) and vanillin (2.0 g/L). Furthermore, M. caribbica SSA1654 could grow in the presence of 2.5 g/L acetic acid but grew moderately. Furfural and formic acid had a significant inhibitory effect on lipid accumulation by M. caribbica SSA1654, compared to the other lignocellulose degradation inhibitors tested. On the other hand, a new MnP-producing oleaginous yeast consortium designated as NYC-1 was constructed. This consortium demonstrated effective decolorization of all individual azo dyes tested within 24 h, up to a dye concentration of 250 mg/L. The NYC-1 consortium's decolorization performance against Acid Orange 7 (AO7) was investigated under the influence of several parameters, such as temperature, pH, salt concentration, and co-substrates (e.g., carbon, nitrogen, or agricultural wastes). The main physicochemical properties of biodiesel produced by AO7-degraded NYC-1 consortium were estimated and the results were compared to those obtained from international standards. The findings of this study open up a new avenue for using peroxidase-producing oleaginous yeasts inhabiting wood-feeding termite gut symbionts, which hold great promise for the remediation of recalcitrant