The antifungal activity of lauric, myristic and palmitic acids and their monoglycerides against fusaria was investigated. Data were modelled through a re-parameterized Gompertz equation and the Minimum Detection Time (MDT), i.e. the time (days) to attain 1 cm colony diameter, was evaluated. Lauric acid exerted a strong bioactivity against moulds; palmitic and myristic acids and their monoglycerides showed a moderate effectiveness and in a reversible manner. The results of this work could be considered quite promising; however, further investigations are proposed to validate these data in foods.

The effectiveness of lauric, myristic and palmitic acids and their monoglycerides against Escherichia coli O157:H7, Yersinia enterocolitica and Salmonella sp. A total of 20 ppm of myristic and palmitic acids and their monolgycerides showed a promising bioactivity (60-80%) against E. coli O157:H7 within 10-24 h; 50 ppm of monolaurin inhibited Y. enterocolitica and E. coli O157:H7 by >90% of control for 96 h; otherwise, 40 ppm of monolaurin and 30-50 ppm of lauric acid reduced Y. enterocolitica growth by >65% of control. The effect of lauric acid and its monoglyceride against Salmonella spp. was moderate (inhibition of approximately 30%). The results of this paper suggested some interesting ideas: the same compound could exert an inhibition or a stimulation of microbial growth; moreover, the studied compounds seemed to act in a reversible manner, as the inhibition of micro-organism was quite strong within the first 10-24 h and decreased for a prolonged incubation.

The antifungal activity of three fatty acids (lauric, myristic, and palmitic acids) and their monoglycerides (monolaurin, monomyristic acid, and palmitin, respectively) against Aspergillus and Penicillium species in a model system was investigated. Data were modeled through a reparameterized Gompertz equation. The maximum colony diameter attained within the experimental time (30 days), the maximal radial growth rate, the lag time (i.e., the number of days before the beginning of radial fungal growth), and the minimum detection time (MDT; the number of days needed to attain 1 cm colony diameter) were evaluated. Fatty acids and their monoglycerides inhibited mold growth by increasing MDT and lag times. The effectiveness of the active compounds seemed to be strain and genus dependent. Palmitic acid was the most effective chemical against aspergilli, whereas penicilli were strongly inhibited by myristic acid. Aspergilli also were more susceptible to fatty acids than were penicilli, as indicated by the longer MDT.

The metabiotic effects of Fusarium proliferatum, F. avenaceum, and F. oxysporum on Escherichia coli O157:H7 and Listeria monocytogenes in fresh tomatoes were investigated. Tomatoes were preinoculated with the molds and incubated at 15 degrees C for 7 days; then they were inoculated separately with the pathogens, packaged in air and modified atmosphere (5% O2, 30% CO2, and 65% N2), and stored at 4, 8, and 12 degrees C for 9 days. The cell loads of pathogens and lactic acid bacteria and the pH were evaluated periodically. The data were modeled through some different mathematical models to assess the shoulder length, i.e., the time before the beginning of the exponential death phase, the 1-log reduction time (s), and the pathogen death time (deltastand). The preinoculation of tomatoes with the molds enhanced the survival of E. coli O157:H7 by prolonging shoulder length and 8 parameters; this effect, however, was not observed for L. monocytogenes. pH values did not undergo significant changes within the storage time, and the lactic acid bacteria increased from 5 to 7 log CFU/g, without significant differences among the storage temperatures or the packaging atmospheres. The results of this research showed that the use of fresh tomatoes colonized by fusaria (even if the contamination is not visible) could increase significantly the risk of outbreaks due to some pathogens that could be on the surface of fruits and vegetables as a result of cross-contamination at home or incorrect postharvest operations.

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Plant litter decomposition is critical for terrestrial ecosystem productivity. Poa ligularis Nees ex Steud and Nassella tenuis (Phil.) Barkworth are native, desirable perennial grasses in central Argentina’s rangelands. Amelichloa ambigua (Speg.) Arriaga & Barkworth is only consumed when a better forage is unavailable. Litter traps were used to collect aboveground litter during two years. In March 2012, six bags, each one containing either leaf blade (three bags, one per species) or root litter (three bags, one per species) of the three species were located below the canopy of each replicate plant of the studied species (hereafter referred to as ‘location’). Blade litter bags were located on the soil surface, and root litter bags buried at 10cm soil depth. This allowed evaluation of the effects of defoliation, the different species canopies and the microbial community activity around their roots on decomposition of above- and belowground litter. For each species, twenty plants were either defoliated twice (5cm stubble height) or remained undefoliated during the growing season. Litter bags were collected after 2, 7, 13 and 24 months incubation. The study was repeated in 2013, with additional bags were placed for N content determination on leaf blade and root litters. Aboveground litter production was highest in P. ligularis; however, no differences were observed among species when the effect of plant size was eliminated. Aboveground litter of desirable species had higher N content and decomposed faster than that of A. ambigua. The opposite was recorded for root litter. Defoliation had no effect on litter decomposition, but location effects were detected after one year of incubation. Desirable perennial grasses promoted organic matter loss from litter, a key factor in increasing soil fertility in this semiarid ecosystem.

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