Degradation capability of Acinetobacter indicus LXX12 on tobacco straw and its whole genome analysis

A high-efficiency tobacco straw-degrading strain, Acinetobacter indicus LXX12, was isolated from tobacco-planting soil in Anshun City, Guizhou Province, China. Systematic investigations were conducted on its physiological and biochemical characteristics, environmental adaptability, and degradation mechanisms. The strain is a Gram-negative, non-motile aerobic bacterium capable of tolerating extreme conditions, including a pH range of 6-11, salinity up to 10%, and temperatures between 15 °C and 44 °C, while exhibiting notable nicotine tolerance. The strain demonstrated robust cellulolytic activity, with a CMCase activity of 65.25 U/mL after 24 h incubation. Inoculation with LXX12 resulted in a 65.7% weight loss of tobacco straw after 35 days of treatment. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed its synergistic degradation of cellulose, hemicellulose, and lignin. Whole-genome sequencing revealed that the strain's genome harbors 65 CAZy enzyme genes, including 11 glycoside hydrolases (GH3 and GH5 family endoglucanases and β-glucosidases) for cellulose degradation, 6 auxiliary redox enzymes (AA3, AA4, and AA6 family vanillyl alcohol oxidases and 1,4-benzoquinone reductases) for lignin modification, as well as CE3 acetylxylan esterases and CBM50 substrate-binding modules. These enzymes collectively form a "backbone depolymerization-side chain modification-redox-driven" multi-enzyme synergistic network. KEGG pathway analysis further elucidated its capability to convert lignin derivatives into carbon sources via benzoate degradation, glycolysis, and the tricarboxylic acid (TCA) cycle. Based on 16 S rDNA sequence alignment, the strain showed 99.78% similarity to Acinetobacter indicus CIP 110,367 strain A648, and was designated Acinetobacter indicus LXX12 despite notable phenotypic discrepancies. The isolation and functional characterization of this strain provide a novel microbial resource for lignocellulose bioconversion, combining high efficiency with environmental adaptability, and hold significant potential for agricultural waste valorization.

Integrated Ozonation-Enzymatic Hydrolysis Pretreatment of Sugarcane Bagasse: Enhancement of Sugars Released to Expended Ozone Ratio

The combined effects of three key ozonation process parameters on the integrated ozonation-enzymatic hydrolysis pretreatment of sugarcane bagasse (SCB) were investigated, with emphasis on the relationship between sugar release and ozone consumption. A lab-scale fixed bed reactor was employed for ozonation at varying ozone doses (50, 75 and 100 mg O3/g SCB), particle sizes (420, 710 and 1000 µm) and moisture contents (30, 45 and 60% w/w) in multifactorial experiments, keeping a residence time of 30 min. The ozonated SCB showed a reduction in the content of acid-insoluble lignin from 26.6 down to 19.1% w/w, while those of cellulose and hemicellulose were retained above 45.5 and 13.6% w/w, with recoveries of 100–89.9 and 83.5–72.7%, respectively. Ozone-assisted enzymatic hydrolysis allowed attaining glucose and xylose yields as high as 45.0 and 37.8%, respectively. The sugars released/ozone expended ratio ranged between 2.3 and 5.7 g sugars/g O3, being the higher value achieved with an applied ozone input of 50 mg O3/g SCB and SCB with 420 µm particle size and 60% moisture. Such operating conditions led to efficient ozone utilization (<2% unreacted ozone) with a yield of 0.29 g sugars/g SCB. Overall, the amount of sugars released relative to the ozone consumed was improved, entailing an estimated cost of ozonation of USD 34.7/ton of SCB, which could enhance the profitability of the process.