DEGRADATION

Microbial degradation of emulsion paints poses significant challenges in industrial and environmental settings, often leading to discoloration, structural breakdown, and reduced durability of coated surfaces. Among the key microbial agents, Bacillus spp. and Escherichia coli have been identified for their enzymatic capabilities and metabolic versatility in degrading paint components such as binders, pigments, and additives. These bacteria utilize organic compounds in paint as carbon sources, contributing to biodeterioration through acid production, biofilm formation, and enzymatic hydrolysis. This study presents a comparative analysis of the physiological and growth responses of Bacillus spp. and Escherichia coli over a 21-day incubation period under ambient laboratory conditions. Key parameters monitored included pH, optical density (OD), temperature, and total viable count (TVC), providing insights into microbial adaptation and proliferation trends. For Bacillus, the pH remained stable at 7.0 until Day 7, then declined to 6.0 by Day 14, suggesting increased metabolic activity and acid production, followed by a slight recovery to 6.2. OD values fluctuated, peaking at Day 14 (0.40), indicating active biomass accumulation, while TVC rose progressively from 0.675 ×10⁷ CFU/mL to 9.60 ×10⁷ CFU/mL by Day 21, reflecting robust growth. Temperature varied modestly between 24°C and 27°C, with no apparent inhibitory effect. In contrast, E. coli
exhibited a sharper pH decline from 6.8 to 5.6 by Day 14, consistent with its fermentative metabolism. OD decreased steadily from 0.51 to 0.26, suggesting reduced cell density or viability over time. However, TVC increased significantly, from 0.5 ×10⁷ CFU/mL to 8.35 ×10⁷ CFU/mL, indicating sustained proliferation despite declining OD. Temperature ranged from 26°C to 30°C, with peak microbial activity observed at higher temperatures. The results highlight distinct metabolic and growth profiles between the two species. Bacillus demonstrated resilience and biomass recovery, while E. coli maintained high cell counts despite reduced optical density. These findings underscore the importance of multi-parameter monitoring in microbial ecology and have implications for bioprocess optimization, environmental microbiology, and industrial fermentation systems.