The antimicrobial capability of chitosan from Tenebrio molitor as compared with chitosan from crustacean (Penaeus monodon) on different pathogenic microorganisms of concern in food safety was studied. The antimicrobial effect was tested at pH 5 and pH 6.2 and at two different initial concentrations (103 or 106 CFU/mL). Results indicated that chitosan from both sources have antimicrobial activity, although the effect depended on the microorganism considered (Salmonella Typhimurium, Listeria monocytogenes and Escherichia coli O157:H7). Our results indicated that Salmonella was the most resistant bacteria, and that chitosan from insect was less active than chitosan from crustacean, especially against Salmonella. Another important factor on antimicrobial activity was the pH of the sample. When chitosan was added to a solution with a pH of 6.2 it was more active against Listeria and Escherichia coli, than at pH 5.00. Besides, the effect of chitosan appears to decrease with the incubation time, since some increases in counts were observed on E. coli and Salmonella after the 24 and 49 hours of incubation.

The main objective of this work was to study the antimicrobial effect of a cauliflower by-product infusion into an affordable in vivo model (Caenorhabditis elegans). The infusion demonstrated some protective effect on non-infected and infected worms with Salmonella Typhimurium as indicated by higher survival percentile values (75, 50, 25, and 5% percentiles) as compared with those from worms unexposed to the infusion. The antimicrobial effect of the infusion was evaluated on Salmonella intestinal colonization of infected worms (24, 48, and 96 h post-infection). At 96 h post-infection, the concentration of Salmonella was reduced around 2 log cycles in infected cauliflower treated group (p < 0.05) as compared with infected non-cauliflower group. Here we show that cauliflower by-products extend survival and have an antimicrobial effect in an in vivo nematode model, C. elegans, as a previous validation step to longer and costlier farm animal studies.