Influence of substrate/inoculum ratio, inoculum source and ammonia inhibition on anaerobic digestion of poultry waste.

Poultry wastes are rich in organic matter, allowing their use as substrates for biogas production by anaerobic digestion (AD). The major difficulty in the anaerobic digestion of this protein-rich waste is ammonia inhibition. Different results of biochemical methane potential (BMP) were obtained after the mesophilic anaerobic digestion of different avian waste in batch mode. It was shown that using two different inoculum (Liger and Saint-Brieuc) sources and different substrate-to-inoculum (S/I) ratios does not have a significant effect on the biochemical methane potential of organic laying hen droppings (OLHD); an average of 0.272 Nm3 CH4·kg-1·VS was obtained with both inocula. Otherwise, it affects the hydrolysis constant KH, and it decreases when the substrate-to-inoculum ratio increases. Furthermore, Liger is the most suitable inoculum for our substrate because it shows stability during the process even with different organic loads. Comparing the biochemical methane potential of multiple avian wastes such as organic laying hen droppings and different slaughterhouse waste highlights the importance of slaughterhouse waste in the anaerobic digestion process because of the high methane yield observed especially with the viscera (0.779 Nm3 CH4·kg-1 VS, SD = 0.027 Nm3 CH4·kg-1 VS). Moreover, methane production was affected by increasing the ammonia concentrations; when [N-NH3] > 9.8 g·N-NH3·L-1, the biochemical methane potential decreases and the lag phase increases (λ > 30 days); a total inhibition of the process was observed when ammonia concentration is above 21.8 g·L-1.

Prediction of Salmonella serovars isolated from clinical and food matrices in Lebanon and genomic-based investigation focusing on Enteritidis serovar.

Salmonella enterica subsp. enterica serovars are considered major causes of food poisoning and we performed this study because Salmonella is a burden in Lebanon. The present study investigated the ability of genomic information to predict serovar using a collection of Salmonella isolates from infected humans (n = 24) and contaminated food (n = 63) in Lebanon. Further, the phylogenomic relationships of the serovar the predominated in Lebanon (i.e., S. Enteritidis; n = 25) were investigated in comparison with isolates from other countries (n = 130) based on coregenome single nucleotide polymorphisms (SNPs). Genetic elements, specifically Salmonella pathogenicity islands (SPIs), plasmid replicons, and antibiotic-resistance genes were screened in S. Enteritidis genomes (n = 155). Our results revealed that the Salmonella serovars identification by seroagglutination from the samples isolated in Lebanon (n = 87) was highly correlated with the genomic-based prediction of serovars (80.4-85.0% with SeqSero1 and 93.1-94.2% with SeqSero2). The Salmonella serovars isolated from human and food samples in Lebanon were mainly Enteritidis (28.7%) and Infantis (26%). To a rare extent, other serovars included Amager, Anatum, Bredeney, Chincol, Heidelberg, Hofit, Kentucky, Montevideo, Muenster, Newport, Schwarzengrund, Senftenberg and Typhimurium. In comparison with other countries, S. Enteritidis samples isolated in Lebanon (56 ± 27 intra-group pairwise SNP differences) presented a strong phylogenomic relativeness at the coregenome level with samples, as for example with samples isolated from Syria (65 ± 31 inter-group pairwise SNP differences). Most of the studied S. Enteritidis genomes encoded 10 SPIs involved in survival in immune cells (i.e. SPIs 1, 2, 3, 4, 5, 12, 13, 14, 16 and 17). The plasmid replicons IncFIB (S)_1 and IncFII (S)_1 encoding elements involved in virulence were identified in the majority of the S. Enteritidis genomes (94% and 96%, respectively), the majority exhibiting aminoglycosides (gene aac(6')-Iaa_1). The IncI_1_Alpha replicon responsible for ampicillin-resistance was only detected in 2 of 25 S. Enteritidis Lebanese strains. Genomic-based risk assessment of Salmonella serovars in Lebanon showed that food imported from Syria might be an origin of the S. Enteritidis human cases in Lebanon. The detection of several SPIs involved in the survival, plasmid replicons involved in virulence, and aminoglycoside-resistance genes, emphasizes that S. Enteritidis is of paramount importance for public health in Lebanon and other countries.