Two enzyme-linked immunosorbent assay (ELISA) kits were evaluated for their effectiveness in detecting and differentiating between Shiga toxin 1 and 2 (Stx1 and Stx2) produced by Shiga toxin-producing E. coli (STEC) inoculated into food and water samples. Each kit incorporated monoclonal antibodies previously determined to bind all known Stx1 or Stx2 subtypes with the exception of Stx2b. Four different sample types, including ground beef, Romaine lettuce, pond water, and pasteurized milk were inoculated with Stx1a-, Stx2a-, or Stx1a- and Stx2a-producing STEC strains, enriched using modified tryptic soy broth (containing mitomycin C) for 6, 16, and 22 h, and tested using the ELISA kits in the presence of a bacterial protein extraction reagent (B-PER™). The two Shiga toxin types were readily detected and distinguished for all tested sample types. There was good overall sensitivity, specificity, variance, and reproducibility for the two ELISA kits and they should prove useful for application in food testing.

The purpose of this study was to investigate the difference in expression of fatty acid biosynthesis genes and survival of different serotypes of Salmonella when incubated in a low‐water‐activity (aw) food over a 14‐day period. Stationary cells of five strains of Salmonella enterica belonging to 3 different serovars (Typhimurium ATCC 2486, Enteritidis H4267, Tennessee ARI‐33, Tennessee S13952 and Tennessee K4643) were inoculated into granular sugar (aW = 0·50) and held aerobically over a 14‐day period at 25°C. Survival was determined by enumerating colonies on TSA and XLT‐4 plates at 0, 1, 3, 5, 7 and 14 days. Correspondingly, gene expression was evaluated for three selected genes involved in fatty acid biosynthesis and modification (fabA, fabD and cfa). After 14 days of incubation, the population was reduced from 2·29 to 3·36 log for all five strains. Salmonella Tennessee ARI‐33 and Salm. Tennessee K4643 displayed greater survival than Salm. Typhimurium and Salm. Enteritidis. The increased expression of the cfa gene (involved in cyclopropane fatty acid biosynthesis) over 14 days was found associated with strains with a lower survival rate. The fabA gene (involved in unsaturated fatty acid biosynthesis) was observed up‐regulated for all strains for at least one sampling time and for Salm. Tennessee ARI‐33 for all time points tested, suggesting its potential role in enhancing Salmonella survival in low awfoods. SIGNIFICANCE AND IMPACT OF THE STUDY: Numerous outbreaks of salmonellosis associated with low‐water‐activity foods have been reported. Therefore, the adaptive mechanisms utilized by Salmonella to survive in low‐water‐activity foods for prolonged periods of time need to be better understood. The results in this study showed that low‐water‐activity environments increase expression of gene fabA, which is involved in unsaturated fatty acid biosynthesis of Salmonella, while the increased expression of cfa, associated with cyclopropane fatty acid synthesis, was associated with decreased survival over 14 days.

The global food demand is projected to significantly increase. To maintain global food security in the future, protein production needs to become more efficient regarding the use of limited land and water resources. Protein-rich biomass can be produced via direct air capture of CO2 with the help of H2-oxidizing bacteria and renewable electricity in a closed, climate-independent system. This quantitative literature review conservatively estimated the direct land and water use of bacterial protein production relying on secondary data for the components of the technology and for the reference protein sources. A several times higher potential protein yield per land area can be achieved by this technology with approximately one-tenth of the water use compared to that required for soybean production.

Twelve ruminally, duodenally, and ileally-cannulated Hereford heifers (average initial BW 313 +/- 20 kg) were used in a replicated experiment to evaluate dairy food processing wash water solids (WWS) as a protein source. Heifers were fed 2.8 kg of chopped (7.6 cm) hay and one of three supplements (1.5 kg/d, DM basis). Supplements were formulated to be similar in energy and contained 1.0 (control), 23.2 (WWS), and 21.6% (soybean meal; SBM) CP on an OM basis. Total N and nonammonia N entering the duodenum (g/d) were greater (P <. 10) for heifers fed WWS and SBM supplements than for controls. Bacterial N flow (g/d) at the duodenum was less (P < .10) for controls (43.9) than for WWS- (63.9) and SBM- (69.9) supplemented heifers. Feed escape N (g/d) was greater (P < .10) for WWS-fed heifers than for those fed SBM (32.1 vs 20.7 g/d, respectively). Total tract N digestion (g/d) was greatest (P < .10) for SBM, intermediate for WWS, and least for control heifers. Microbial protein synthesis (g/kg of OM intake) was enhanced (P < .10) by WWS and SBM supplementation, but efficiency of synthesis (g/kg of OM fermented) did not differ among treatments. Essential amino acid (AA) disappearance in the small intestine (g/d) was less (P < .10) for control than for the other two treatments. Nonessential AA disappearance was greatest (P < .10) for the WWS and least (P < .10) for the control treatment. Based on our short-term feeding data, WWS can be used as a protein source for ruminants, but N availability of WWS seems less than that of soybean meal.