Harmful algal blooms are natural phenomena caused by the massive growth of phytoplankton that may contain highly toxic chemicals, the so-called marine biotoxins causing illness and even death to both aquatic organisms and humans. Their occurrence has been increased in frequency and severity, suggesting a worldwide public health risk. Marine biotoxins can accumulate in bivalve molluscs and regulatory limits have been set for some classes according to European Union (EU) legislation. These compounds can be distinguished in water- and fat-soluble molecules. The first group involves those of Paralytic Shellfish Poisoning and Amnesic Shellfish Poisoning, whereas the toxins soluble in fat can cause Diarrhoeic Shellfish Poisoning and Neurotoxic Shellfish Poisoning. Due to the lack of long-term toxicity studies, establishing tolerable daily intakes for any of these marine biotoxins was not possible, but an acute reference dose can be considered more appropriate, because these molecules show an acute toxicity. Dietary exposure assessment is linked both to the levels of marine biotoxins present in bivalve molluscs and the portion that could be eaten by consumers. Symptoms may vary from a severe gastrointestinal intoxication with diarrhoea, nausea, vomiting and abdominal cramps to neurological disorders such as ataxia, dizziness, partial paralysis and respiratory distress. The official method for the detection of marine biotoxins is the mouse bioassay (MBA) showing some limits due to ethical restrictions and insufficient specificity. For this reason, the liquid chromatography-mass spectrometry method has replaced MBA as the reference technique. However, the monitoring of algal blooms producing marine biotoxins should be regularly assessed in order to obtain more reliable, accurate estimates of bloom toxicity and their potential impacts.

Editorial: Biogenic amines in foods

Flocculation is an important feature for yeast survival in adverse conditions. The natural diversity of flocculating genes in Saccharomyces cerevisiae can also be exploited in several biotechnological applications. Flocculation is mainly regulated by the expression of genes belonging to the FLO family. These genes have a similar function, but their specific contribution to flocculation ability is still unclear. In this study, the distribution of FLO1, FLO5 and FLO8 genes in four S. cerevisiae wine strains was investigated. Subsequently, both FLO1 and FLO5 genes were separately deleted in a flocculent S. cerevisiae wine strain. After gene disruption, flocculation ability and agar adhesion were evaluated. FLO1 and FLO5 genes inheritance was also monitored. All strains presented different lengths for FLO1 and FLO5 genes. Results confirm that in S. cerevisiae strain F6789, the FLO5 gene drives flocculation and influences adhesive properties. Flocculation ability monitoring after a cross with a non-flocculent strain revealed that FLO5 is the gene responsible for flocculation development.

The influence of calf (R1), kid (R2) and pig (R3) rennets on microbiota, biogenic amines (BAs) and γ-aminobutyric acid (GABA) accumulation in raw milk ewe’s cheeses was evaluated. Cheeses were investigated at different ripening times for their microbial composition, free amino acids (FAAs), BAs and GABA content. Moreover, the expression of tyrosine (tdc) and histidine (hdc) decarboxylases genes was evaluated by quantitative Real Time–Polymerase Chain Reaction (qRT-PCR). Microbial counts showed similar values in all samples. Pig rennet were cheeses were characterized by higher proteolysis and the highest values of BAs. The BAs detected were putrescine, cadaverine and tyramine, while histamine was absent. qRT-PCR confirmed this data, in fact hdc gene was not upregulated, while tdc gene expression increased over time in agreement with the increasing content of tyramine and the highest fold changes were detected in R3 cheeses. GABA showed the highest concentration in R2 cheeses reaching a value of 672 mg/kg. These results showed that the accumulation of BAs and GABA in Pecorino di Farindola is influenced by ripening time and type of coagulant. Further studies are required to develop starter cultures to reduce BAs content and improve health characteristics of raw milk ewe’s cheeses.