BACKGROUND The present study compared the performance and capability of thermophilic–mesophilic, temperature‐phased anaerobic digestion (TPAD) of wastewater sludge at 45 and 55 °C in terms of rate of hydrolysis and methanogenesis at two point interval times – December and January – with operational conditions kept constant (total solid content 6.5%, solids retention time 12.5 days). RESULTS The reduction of volatile solids (VS) was 77% at 45 °C TPAD‐1 and 72% at 55 °C TPAD‐II. The accumulation of ammonia and volatile fatty acids (VFAs; propionic acid) were observed to be below the inhibitory range (>3000 mg L−1), whereas the methane (CH4) production (45 °C, 3.55 ± 0.47 L CH4 L−1 day−1; 35 °C, 1.44 ± 0.12 L CH4 L−1 day−1) remained considerably higher in TPAD‐I than TPAD‐II. Furthermore, the TPAD‐II system suffered from certain degree of instability due to high level of total VFAs (6087 ± 1578 mg L−1), low buffering capacity, increased level of total NH3 (2982 ± 219 mg L−1) and free NH3 (246 ± 25 mg L−1), and relatively reduced CH4 production (1.69 ± 0.1 L L−1 day). The bacterial and archaeal population of the TPADs investigated by 454 pyrosequencing and Illumina sequencing showed, in both TPAD systems, a bacterial community dominated by Firmicutes, followed by Bacteriodetes, Proteobacteria, Synergistetes and Actiniobacteria. The archaeal community was dominated by Methanimicrobia (74–84% Methanosarcina) and Methanobacteria (15–27% Methanobacterium). A progression from genus Clostridium to Coprothermobacter and Tepidanaerobacter, and Methanocarcina to Methanothermobacter and Methanobacterium was observed in TPAD‐II. CONCLUSIONS This study proved the processes driving the dynamics of key microbial population and its correlation with hydrolytic functionality of TPAD systems. © 2019 Society of Chemical Industry

This study demonstrates the inhibition of selective foodborne pathogenic bacteria by exposure to a 355 and 266 nm Nd:YAG laser. In baseline assay P. aeruginosa showed maximum inhibition followed by Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, and Listeria monocytogenes grown on agar surface. Cell lysis was confirmed by confocal microscopy for all pathogens. In liquid media, P. aeruginosa was irradiated with the third harmonic of a Nd:YAG laser pulse energy of 185 mJ, which was able to reduce the population of 1.65 × 105 by 4.7 logs, while P. aeruginosa could only be reduced by 0.73 log/cm2 on packaging material surface. In the final phase, the laser’s potential was preliminarily tested for sterilization of raw cow milk. The reduction patterns of E. coli, Salmonella sp. yeasts and Lactobacillus sp. were 30%, 25%, 47%, and 30%, respectively, in raw milk, moreover, laser exposure had no significant impact on physio-chemistry of milk. Therefore, results indicate the potential application of laser in packing materials and milk sterilization at the industrial level.

Salads are considered healthy food but poor hygienic practices may destroy the quality of salads. The poor quality salads may cause health issues if consumed. A study was carried out to monitor microbiological quality of salads. Samples (n=90) were collected from road side venders, fast food outlets and family restaurants (30/each type), in different localities in Lahore. Samples were processed to determine aerobic bacterial, coliform and fungal counts. The highest mean bacterial count (9.64±2.43), coliform (9.57±2.79) and fungal counts (2.51±2.62) were observed in salads from road side venders. According to the International Commission on Microbiological Specifications for Foods (ICMSF) 73.33 percent of salad samples by bacterial, 98 from coliform and 26.67 by fungal counts were found unacceptable for human consumption. Among isolated bacteria were identified as Staphylococcus aureus, Escherichia coli, Klebsiells, Salmonella, Enterobacter, Aeromonas and Bacillus. The predominant fungal species in salads were Aspergillus fumigatus, Aspergillus niger and Aspergillus flavus. A. fumigatus is an obligate pathogen and Aflatoxin (B1 and B2) produced by A. flavus cause of mycotoxicosis. It was concluded that the salads from road side venders are source of bacteria and fungi having potential for toxins production.