In the process of converting lignocellulose to biofuels, lignin is one of the major obstacles. To overcome this recalcitrance, exploring bacteria with higher delignification efficiency or novel enzymes has been highlighted. In this study, eight bacteria isolated from termite guts were evaluated for their lignolytic potential. Among the isolates, Raoultella ornithinolytica MP-132 was selected for further investigation based on its capacity to use a broad range of monomeric and dimeric aromatic compounds as carbon source. Subsequently, the structural evolution of milled wood lignin (MWL) was evaluated by FTIR and TGA. The analysis results showed the cleavage of various chemical linkages, destruction of aromatic ring structures, side-chain oxidation and demethoxylation or demethylation by comparing the different peak intensities in the corresponding curve of each sample. In addition, the thermal stability of MWL increased after bacteria treatment, indicating the structural change in MWL caused by treatment with strain MP-132. These results demonstrated that Raoultella ornithinolytica MP-132 may be a potential candidate for the lignocellulosic bioenergy industry.

Chitin is the second most abundant natural renewable biomass, widely present in seafood waste. Nevertheless, its crystalline structure makes processing difficult. Ectoine, a high value compatible solute, is common in pharmaceuticals and cosmetics. However, direct ectoine production from chitinous waste using wild-type microbial strains is rarely reported. Here, we show that Vibrio diabolicus X511 possesses a complete ectoine biosynthetic gene cluster (ectABC-ask) as well as native chitinolytic genes. These genomic features are consistent with the strain’s ability to directly ferment colloidal chitin, crab shell flakes, and shrimp shell powder for ectoine production, eliminating the need for exogenous chitinase supplementation. With 5 g/L yeast extract as the nitrogen source, strain X511 produced 2.172 g/L ectoine from colloidal chitin, a titer comparable to, or even higher than, those reported for several wild-type strains grown on soluble carbon sources. Using highly crystalline crab shell flakes and raw shrimp shell powder as substrates, the strain achieved titers of 0.259 g/L and 0.181 g/L respectively, accompanied by substrate weight losses of 60% and 43.47%. FESEM, XRD, and FTIR analyses confirmed the strain’s capacity to effectively disrupt crystalline structure of chitin and degrade raw shrimp shell biomass. These findings suggest that X511 may be a promising biocatalyst for the effective bioconversion of chitinous waste to high value chemicals.