BackgroundEffects of organic acids on microbial fermentation are commonly tested in investigations about metabolic behaviour of bacteria. However, they typically provide only descriptive information without modelling the influence of acid concentrations on bacterial kinetics.ResultsWe developed and applied a mathematical model (secondary model) to capture the toxicological effects of those chemicals on kinetic parameters that define the growth of bacteria in batch cultures. Thus, dose-response kinetics were performed with different bacteria (Leuconostoc mesenteroides, Carnobacterium pisicola, Escherichia coli, Bacillus subtilis and Listonella anguillarum) exposed at increasing concentrations of individual carboxylic acids (formic, acetic, propionic, butyric and lactic). In all bioassays the acids affected the maximum bacterial load (Xm) and the maximum growth rate (vm) but only in specific cases the lag phase (λ) was modified. Significance of the parameters was always high and in all fermentations the toxicodynamic equation was statistically consistent and had good predictability. The differences between D and L-lactic acid effects were significant for the growth of E. coli, L. mesenteroides and C. piscicola. In addition, a global parameter (EC50,τ) was used to compare toxic effects and provided a realistic characterization of antimicrobial agents using a single value.ConclusionsThe effect of several organic acids on the growth of different bacteria was accurately studied and perfectly characterized by a bivariate equation which combines the basis of dose-response theory with microbial growth kinetics (secondary model). The toxicity of carboxylic acids was lower with the increase of the molecular weight of these chemicals.

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Recent research has substantially focused on residual subproducts containing chemical compounds with bioactive properties. Even though there are some culinary or medicinal uses of Capsicum seeds, there is still a seed mass waste from pepper processing. Many pepper leading producer countries generally lack the facilities and infrastructure required for such processing technologies and so, pepper seeds are usually either destroyed or employed as landfilling or as animal feed. This involves an inadvertent economic loss for producers as well as a detrimental environmental impact. However, there is a hidden potential within the pepper processing industry related to valorization of pepper seeds to obtain added value by-products and thus reduce generated waste. Pepper seeds are a good source of antioxidants, carotenoids, phenolic acids, flavonoids, and vitamins C, E, and A and are also rich in volatile compounds, among others. The unique alkaloids of this genus are capsaicinoids and capsainoids, which have been linked to many beneficial biochemical and pharmacological effects including anti-oxidative or anti-inflammatory activities. Other prominent bioactive compounds of peppers seeds include saponins, lectins, and polyunsaturated fatty acids. In this context, an overview of the biological properties, extraction systems, and possible industrial application of bioactive compounds of pepper whole fruit and seeds is presented.

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