Characterization and Growth Parameters Optimization of Phenol Degrading Bacteria From Batu Tannery Wastewater

Abstract

Phenolic compounds pose a threat to human and animal health, and the accumulation of phenol introduces toxicity to both flora and fauna, potentially leading to fatal consequences upon high exposure. Despite the availability of various methods for phenolic removal, biodegradation using microorganisms stands out as an environmentally friendly approach. This study aimed at screening, characterizing, and assessing the phenolic removal efficiency of bacteria isolated from tannery wastewater in Addis Ababa, along with the optimization of growth parameters of the phenol degrading isolates. Wastewater samples (500 mL) were collected from Batu Tannery industry using sterile bottles. The screening of phenolic-degrading bacteria isolates (PDBI) was carried out on minimal salt media supplemented with 200-2000 ppm phenol crystal and nitro phenol. The cultures were identified using biochemical and morphological characterization. Optimization and phenolic degradation assay were performed for PDBI. Data were analyzed using Microsoft Excel office (2008), and Origin version 2019b. The results revealed that out of 49 isolates, 8 (PDBI-7, PDBI-9, PDBI-11, PDBI-12, PDBI-15, PDBI-21, PDBI-23, and PDBI 49) isolates were found to be effective in phenols (Phenol crystal and nitrophenol) biodegradation at the concentration of 600-2000 ppm. These isolates were identified as Bacillus subtilis PDBI-9 and Klebsiella pneumoniae PDBI-49. Based on optimization, the maximum Cell Dry Weight (g/l) and OD600 nm recorded for B. subtilis PDBI-9 and K. pneumoniae PDBI-49 at pH 7and 30°C. Glucose gave the maximum Cell Dry Weight (CDW)(g/L) for PDBI-49, whereas mannitol gave the minimum Cell Dry Weight (CDW)(g/L) for PDBI-9. The maximum (0.00867± 0.00031) and minimum (0.00113 ± 0.00021) CDW(g/L) obtained when peptone and KNO3 utilized by PDBI-49 and PDBI-9, respectively. Study showed that K. pneumoniae (PDBI-49) (86.24%) was more effective in degrading phenolic compounds (Phenol crystal and nitrophenol) than B. subtilis (PDBI-9) (76%). In conclusion, B. subtilis PDBI-9 and K. pneumoniae PDBI-4) employed for the phenol biodegradation.