Aflatoxins: Risk, Exposure and Remediation

Aflatoxins family includes a great number of lipophilic molecules produced by aerobic microscopic fungi belonging to the genus Aspergillus. The chapter describes their chemical structure, chemical and physical properties, and aspects related to their presence in food and commodities. Aflatoxins presence in food is considered a real and severe risk to consumers for their toxicity. Aflatoxins levels and frequency of foods natural contamination as reported in the scientific literature are briefly analyzed. Focus is given to the different foodstuffs that may be at risk of contamination by Aspergillus and the subsequent accumulation of aflatoxins in the food chain. Bioavailability and bioaccessibility of aflatoxins will be discussed considering that these unwanted molecules can be assumed by the humans with the diet. Bioaccessibility, that deals with the fraction of micro-nutrients released from the food matrix during digestion and gastro-intestinal available for absorption, will be discussed with reference to aflatoxins bioaccessibility of during the digestion process, considering the relationships between the food matrix and its influences on aflatoxins fate. Bioavailability of the aflatoxins assumed from the diet depends on their stability during digestion, since they are released from the food matrix (bioaccessibility) and on the efficiency of their passage through the gastro-intestinal mucosa. The term bioavailability includes the concepts of availability to the absorption, metabolism, distribution of nutrients to tissues and bioactivity and indicates the fraction of micro-nutrients absorbed by the body and the speed with which these molecules are absorbed and made available at their site of action. Despite of the practical difficulties in measuring the distribution and bioactivity of aflatoxins on a specific human body organ, the bioavailability is the fraction of an oral dose of a compound or precursor of an active metabolite that reaches the bloodstream. Bioaccessibility includes the entire sequence of events that take place during the digestion of food material that can be assimilated by the body through the epithelial cells of the gastro-intestinal mucosa. Aflatoxins are often present in very small amounts or in traces and, for this reason, a part of the chapter addresses the advanced new chromatographic and spectrometric methods described in the literature and applied to research, that can reveal, even in trace amounts, aflatoxins in biological fluids as free form or as by-products, e.g. non-covalent adducts

An exact algorithm for the Partition Coloring Problem

We study the Partition Coloring Problem (PCP), a generalization of the Vertex Coloring Problem where the vertex set is partitioned. The PCP asks to select one vertex for each subset of the partition in such a way that the chromatic number of the induced graph is minimum. We propose a new Integer Linear Programming formulation with an exponential number of variables. To solve this formulation to optimality, we design an effective Branch-and-Price algorithm. Good quality initial solutions are computed via a new metaheuristic algorithm based on adaptive large neighborhood search. Extensive computational experiments on a benchmark test of instances from the literature show that our Branch-and-Price algorithm, combined with the new metaheuristic algorithm, is able to solve for the first time to proven optimality several open instances, and compares favorably with the current state-of-the-art exact algorithm

A note on selective line-graphs and partition colorings

Le PDF est la version soumise de l'auteur datant de janvier 2019We extend a one-to-one correspondence between the set of all colorings of any graph and the set of all stable sets of an auxiliary graph, from graphs to partitioned graphs. This correspondence has an application to Selective Coloring and to Selective Max-Coloring

The Effect of the Introduced Red Wood Ant Formica paralugubris on the Frequency of Ant Nests and First Plesiobiotic Association between Myrmica ruginodis (Nylander, 1846) and Lasius flavus (Fabricius, 1782)

Red wood ants are ecologically dominant species that affect the composition of the invertebrate community. In the past century, one of these species, Formica paralugubris (Seifert 1996), was introduced outside its native area (the Alps), in the Apennines (Italy). Here we investigated the effect of the presence of an introduced population of F. paralugubris on the frequency of nests of other ant species in Abetone, Central Apennines. Ant nests were found only in the area unoccupied by F. paralugubris. In this area, we also found one pleometrotic association between queens of Lasius flavus (Fabricius, 1782) and two plesiobiotic associations, one between Formica fusca (Linnaeus, 1758) and L. flavus and the other one between Myrmica ruginodis (Nylander, 1846) and L. flavus. This latter is the first plesiobiotic relationship reported between these two species, the second reported for M. ruginodis and the 10th for L. flavus. Additionally, this is the first plesiobiotic association reported for the Mediterranean region and Southern Europe