Isolation and selection of bacterial strains capable of degrading starch and accumulating polyphosphate from vermicelli production wastewater

Currently, the issue of water pollution has become alarming worldwide, as numerous food production factories overlook wastewater treatment before discharging into the environment. Therefore, the isolation and selection of potential bacterial strains from wastewater are problems that need attention. The present study has isolated 32 bacterial strains from the wastewater source of the vermicelli production process in Can Tho City, Vietnam. The isolated bacterial strains exhibited various characteristics such as yellow, creamy white, or opaque white colors; convex or raised elevations; and entire or lobate margins, with bacterial colony sizes ranging from 0.5 to 3.5 mm. By performing the agar well diffusion method, the study selected three bacterial strains, P2, P12, and Y9, which demonstrated the ability to degrade starch. In particular, the Y9 strain exhibited the highest reducing sugar content (1.70–4.64 mg/mL) between the 2nd and 8th days of observation. Additionally, the Y11 strain demonstrated the ability to accumulate polyphosphate granules within cells, with the highest content reaching 1.79 mg/L P2O5. Results from the 16S rRNA gene sequencing method combined with several biochemical tests showed that Y9 and Y11 strains corresponded to Chryseobacterium daecheongense and Bacillus velezensis, respectively, with a similarity of 100%.