Potassium and growth-promoting fungi improve the postharvest quality of grape tomato / Potássio e fungos promotores de crescimento melhoram a qualidade pós-colheita de minitomates

Tomato plants respond well to potassium fertilization, whose insufficiency leads to a drop in fruit production and quality. On the other hand, the association of growth-promoting fungi (GPF) with roots has been shown to be able to optimize nutrient absorption, which implies lower financial costs and a decreased risk of loss of K applied to the soil. The objective of this study was to investigate the effects of inoculation with GPF and K rates on the postharvest quality of grape tomato hybrid 'Mascot' grown in a hydroponic system. The plants were cultivated in a hydroponic drip system using washed and sterilized sand as substrate. They were trained with two stems, leaving three bunches per stem. The experiment was carried out in a splitsplit-plot arrangement in a completely randomized design with three replicates. Ripe fruits were stored for 30 days in PET containers in storage chambers at a temperature of 25 °C. After 0, 10, 20 and 30 days of storage, five fruits were collected to determine the titratable acidity (TA) and soluble solids (SS), reducing sugars (RS) and vitamin C contents. The K rates provided an increase in the quality attributes. At low K rates, inoculation with GPF led to higher TA, SS, RS and vitamin C values. Inoculation of the plants with GPF improved the postharvest preservation of the fruits, especially when the plants underwent nutritional stress during cultivation.(AU)

O tomateiro responde bem à fertilização potássica, cuja insuficiência acarreta queda na produção e qualidade dos frutos. Por outro lado, a associação de fungos promotores de crescimento (FPC) com raízes tem-se mostrado capaz de otimizar a absorção de nutrientes, o que implica menor custo financeiro e menor risco de perdas do K aplicado ao solo. O objetivo deste trabalho foi estudar os efeitos da inoculação com FPC e de doses de K na qualidade pós-colheita do minitomate hibrido Mascot cultivado em hidroponia. As plantas foram cultivadas em sistema hidropônico de gotejamento, usando areia lavada e esterilizada como substrato. Foram conduzidas com duas hastes, deixando-se três cachos por haste. O experimento foi realizado em parcelas sub-subdividadas e em delineado inteiramente ao acaso, com três repetições. Os frutos maduros foram armazenados por 30 dias em embalagens PET em câmaras de armazenamento à temperatura de 25°C. Após 0, 10, 20 e 30 dias de armazenamento coletaram-se 5 frutos para determinação do teor de sólidos solúveis (SS), acidez titulável (AT), de açúcares redutores (AR) e vitamina C. As doses de K tiveram efeito crescente nos atributos de qualidade. Em baixas doses de K a inoculação com FPC resultou em maiores valores de SS, AT, AR e vitamina C. A inoculação das plantas com FPC promoveu melhor conservação dos frutos na pos-colheita, especialmente quando as plantas sofreram estresse nutricional durante o cultivo.(AU)

Multi-enzyme complex of white rot fungi in saccharification of lignocellulosic material

The multi-enzyme complex (crude extract) of white rot fungi Pleurotus ostreatus, Pleurotus eryngii, Trametes versicolor, Pycnosporus sanguineus and Phanerochaete chrysosporium were characterized, evaluated in the hydrolysis of pretreated pulps of sorghum straw and compared efficiency with commercial enzyme. Most fungi complexes had better hydrolysis rates compared with purified commercial enzyme.(AU)

Lignocellulolytic enzyme production of Pleurotus ostreatus growth in agroindustrial wastes

The mushroom Pleurotus ostreatus has nutritional and medicinal characteristics that depend on the growth substrate. In nature, this fungus grows on dead wood, but it can be artificially cultivated on agricultural wastes (coffee husks, eucalyptus sawdust, corncobs and sugar cane bagasse). The degradation of agricultural wastes involves some enzyme complexes made up of oxidative (laccase, manganese peroxidase and lignin peroxidase) and hydrolytic enzymes (cellulases, xylanases and tanases). Understanding how these enzymes work will help to improve the productivity of mushroom cultures and decrease the potential pollution that can be caused by inadequate discharge of the agroindustrial residues. The objective of this work was to assess the activity of the lignocellulolytic enzymes produced by two P. ostreatus strains (PLO 2 and PLO 6). These strains were used to inoculate samples of coffee husks, eucalyptus sawdust or eucalyptus bark add with or without 20 % rice bran. Every five days after substrate inoculation, the enzyme activity and soluble protein concentration were evaluated. The maximum activity of oxidative enzymes was observed at day 10 after inoculation, and the activity of the hydrolytic enzymes increased during the entire period of the experiment. The results show that substrate composition and colonization time influenced the activity of the lignocellulolytic enzymes.(AU)