Characterization and Functional Analysis of Bacillus aryabhattai CY for Acrylic Acid Biodegradation: Immobilization and Metabolic Pathway

Acrylic acid has been widely used in various industrial applications but is harmful to human health and the environment. A novel and efficient degrading acrylic acid bacterium was isolated and identified as Bacillus aryabhattai CY. In this study, batch experiments were conducted to evaluate the biodegradation of acrylic acid by B. aryabhattai CY, which were immobilized in calcium-alginate beads under different conditions. The components of the alginate beads were optimized by the response surface method, and the degradation performance of the immobilized cells was determined. Relative to the free cells, experiment results showed that the immobilized cells can achieve complete degradation of 100 mg/L acrylic acid in 24 h under the optimal conditions of SA 6% (w/v), CaCl2 1% (w/v), and immobilization time of 6 h. According to Haldane’s model, the maximum specific growth rate (μmax) of the free cells and immobilized cells were 0.165/h and 0.210/h, respectively. Experiment data revealed that acrylic acid showed an inhibitory effect on biodegradation by B. aryabhattai CY, especially at concentration higher than 100 mg/L. Furthermore, the reusability of the immobilized cells revealed that the acrylic acid removal rate was above 93.70% within the eight cycles. The immobilized cells also showed higher removal efficiencies in wider ranges of temperature (20°C–60°C) and pH (5.0–10.0) than the free cells. Moreover, the possible degradation intermediates were proposed during the biodegradation of acrylic acid by GC-MS analysis. Results indicated that immobilized beads might have a potential environmental implication in the purification of practical acrylic acid wastewater.