Isolation of agar-degrading Bacillus sp. AT6 and preliminary application for seaweed saccharification

Background: Agar is a common polysaccharide found in nature. However, agar is strongly resisted to the degradation processing, leading to limitation of its application in various areas. Thus, finding an effective solution for agar saccharification significantly improves the economically effects of agar based substrates.Methods: Soil samples were collected from TienPhong Forestry Ltd. Company, ThuyXuan District, ThuaThien Hue province, Vietnam. Potential agar degrading bacteria were screened on a mineral salt agar medium. The isolate was identified based on 16S rRNA nucleotide sequence, morphological, physiological, and biochemical characteristics. Agarase production was evaluated by modification culture conditions including incubation time, shaking speed, and initial inoculum size. Molecular mass of extracellular agarase was determined by native SDS-PAGE. The effect of pH, temperature, metal ions, and organic solvents were performed to characterize the enzyme. Application of enzyme was investigated on seaweed saccharification.Results: An agar degrading bacterial strain was isolated from soils and identified as Bacillus sp. AT6. Maximal agarase accumulation obtained in the culture containing an inoculum size of 10% (v/v), shaking speed of 210 rpm, and 96 hours incubation. The agarase revealed a single band on zymogram analysis with an apparent molecular weight of 180 kDa. The optimal temperature and pH were 40°C and pH 8.0, respectively. All tested metal ions and organic solvents partially decreased enzyme activity. Treating seaweed with agarase resulted in reducing sugars release present in the reaction, indicating the saccharification of seaweed was successful.Conclusion: Bacillus sp. AT6 is a new report of agarolytic bacteria that produces extracellular agarase enzymes. The present results promise strain AT6 is a great candidate for agar saccharification for industrial application.Keywords: Agar degrading bacterium; Agarase; Hydrolysis, hydrolyzed products; Soil bacteria Editorial Expression of Concern20 June 2025: Following publication of this paper, the internal audit (consequent to concerns on quality raised by Web of Science) notified Advancements in Life Sciences about problems in use of English language. By this Editorial Expression of Concern, we alert the scientific community as we address the errors.Editorial Note:26 June 2025: You are viewing the latest version of this article having minor corrections related to the use of English language. Expression of concern is hereby revoked.