Cladosporium cladosporioides LPSC 1088 produces the 1,8-dihydroxynaphthalene-melanin-like compound and carries a putative pks gene.

Cladosporium cladosporioides is a dematiaceous fungus with coloured mycelia and conidia due to the presence of dark pigments. The purpose of this study was to characterize the dark pigments synthetized by Cladosporium sp. LPSC no. 1088 and also to identify the putative polyketide synthase (pks) gene that might be involved in the pigment biosynthesis. Morphological as well as molecular features like the ITS sequence confirmed that LPSC 1088 is Cladosporium cladosporioides. UV-visible, Fourier Transform Infrared (FTIR) and Electron Spin Resonance (ESR) spectroscopy analysis as well as melanin inhibitors suggest that the main dark pigment of the isolate was 1,8 dihydroxynaphthalene (DHN)-melanin-type compound. Two commercial fungicides, Difenoconazole and Chlorothalonil, inhibited fungal growth as well as increased pigmentation of the colonies suggesting that melanin might protect the fungus against chemical stress. The pigment is most probably synthetized by means of a pentaketide pathway since the sequence of a 651 bp fragment, coding for a putative polyketide synthase, is highly homologous to pks sequences from other fungi.

Low intensity light treatment improves purple kale (Brassica oleracea var. sabellica) postharvest preservation at room temperature.

Purple Kale is a vegetable of the Brassicaceae family whose are popularly consumed in recent years due to their high level of healthy components. For consumption, matures leaves are harvested and postharvest senescence is induced. Changes in color leaves due to chlorophyll degradation are the main visible symptoms of postharvest senescence, but there are other changes that affect the nutritional quality of kale. The aim of this study was to investigate if low intensity light pulses could be used to delay postharvest senescence of purple kale stored at room temperature. Daily treatments with 1 h pulses of white or red light were performed. Irradiated samples had approximately 40% higher chlorophyll and protein and more of 20% higher antioxidant capacity and soluble sugar content than control samples regardless of light quality used in treatment (white or red). Both light treatments improve the appearance and quality of kale during storage at room temperature.

Melanins from two selected isolates of Pseudocercospora griseola grown in-vitro: Chemical features and redox activity.

Pseudocercospora griseola is the causal agent of Angular Leaf Spot (ALS), a disease of common bean. Due to its coevolution with beans, two major groups have been defined, "Andean" (P. griseola f. griseola) and "Mesoamerican" (P. griseola f. mesoamericana). The aim of this study was to characterize the dark pigment, melanin, synthetized by a selected isolate of each genic group of P. griseola when grown on Potato-dextrose broth. P. griseola f. griseola isolate S3b and P. griseola f. mesoamericana isolate T4 produced 1.7 ±â€¯0.6 and 4.1 ±â€¯0.9 mg of melanin per g of dry biomass, respectively. Although both melanins possessed similar UV-visible absorption spectroscopic pattern, P. griseola f. mesoamericana isolate T4 melanin had a lower UV-visible absorption, higher reducing activity and metal chelating ability than melanin from P. griseola f. griseola isolate S3b. However, when the size of the sample was 10 mg S3b melanin had a higher content of free phenolic groups. Furthermore, cell wall polysaccharides modified in melanin the availability of active phenolic groups, which was dependent on the fungal isolate and the size of the sample. Therefore, the amount and chemical features of melanin as well as its deposition in mycelium walls within isolates is different, which might explain the different pigmentation and physiological behaviours of these representatives of the two groups of P. griseola.