Aspergillus clavatus UEM 04: An efficient producer of glucoamylase and α-amylase able to hydrolyze gelatinized and raw starch.

The best amylolytic activity production by Aspergillus clavatus UEM 04 occurred in submersed culture, with starch, for 72 h, at 25 °C, and 100 rpm. Exclusion chromatography partially purified two enzymes, which ran as unique bands in SDS-PAGE with approximately 84 kDa. LC-MS/MS identified a glucoamylase (GH15) and an α-amylase (GH13_1) as the predominant proteins and other co-purified proteins. Zn2+, Cu2+, and Mn2+ activated the glucoamylase, and SDS, Zn2+, Fe3+, and Cu2+ inhibited the α-amylase. The α-amylase optimum pH was 6.5. The optimal temperatures for the glucoamylase and α-amylase were 50 °C and 40 °C, and the Tm was 53.1 °C and 56.3 °C, respectively. Both enzymes remained almost fully active for 28-32 h at 40 °C, but the α-amylase thermal stability was calcium-dependent. Furthermore, the glucoamylase and α-amylase KM for starch were 2.95 and 1.0 mg/mL, respectively. Still, the Vmax was 0.28 µmol/min of released glucose for glucoamylase and 0.1 mg/min of consumed starch for α-amylase. Moreover, the glucoamylase showed greater affinity for amylopectin and α-amylase for maltodextrin. Additionally, both enzymes efficiently degraded raw starch. At last, glucose was the main product of glucoamylase, and α-amylase produced mainly maltose from gelatinized soluble starch hydrolysis.

Concentração e redistribuição de nutrientes minerais nos diferentes estádios foliares de seringueira / Concentration and redistribution of mineral nutrients at different stages in the development of the Rubber tree leaf

A seringueira na fase adulta possui um crescimento intermitente com o processo de troca de folhas, que é caracterizado pela senescência. Esse é um mecanismo que as árvores utilizam para reciclarem os nutrientes, por meio dos ciclos bioquímico e biogeoquímico. Estudos sobre o ciclo bioquímico são necessários para verificar o comportamento dos nutrientes minerais, nos diferentes estádios foliares, pois a conservação desses é importante, visto que os seringais são implantados em solos de baixa fertilidade. Desse modo, este trabalho teve por objetivo avaliar a dinâmica dos nutrientes minerais, durante os diferentes estádios foliares da seringueira. As folhas utilizadas foram provenientes de plantas do clone RRIM-600, de um seringal localizado em Nepomuceno, MG. Foram selecionadas oito árvores adultas que possuíam folhas nos diferentes estádios (B1, B2, C e D) e as senescentes (Sen.). As folhas nos estádios B1, B2, C e D foram coletadas nos quatro pontos ortogonais e as senescentes foram coletadas no solo após a agitação mecânica dos galhos. Observou-se que os nutrientes N, P, K, S, Cu e Zn diminuíram os seus teores nos diferentes estádios foliares da seringueira. No entanto, para Ca, Mg, B, Fe e Mn, verificarou-se um comportamento inverso. A redistribuição dos nutrientes foi maior para N, P, K e Cu. A ordem relativa dos teores de macronutrientes encontrados nas folhas foi: N>K>Ca>Mg≥S>P e, para os micronutrientes, a ordem foi: Mn>Fe>Zn>B>Cu.

The Rubber tree during its adult phase presents intermittent growth within the leaf exchange process characterized by senescence, which is a nutrient-recycling mechanism used by trees through biochemical and biogeochemical cycles. Studies including biochemical cycles are necessary in order to verify the mineral nutrients' dynamics at different leaf stages. The conservation of such nutrients is very important to optimize the growing conditions for rubber plantations which are located in soils with low fertility. This study aims to evaluate the mineral nutrients' dynamics during different leaf stages of the rubber tree, leaves were collected from the clones of RRIM-600 taken from a rubber tree plantation in Nepomuceno County, State of Minas Gerais, Brazil. Eight adult examples with leaves in different stages: B1, B2, C and D, plus senescent leaves (Sen) were selected for the study. Samples from leaves in stages B1, B2, C and D were taken from the trees at the four orthogonal points; the senescent leaves were collected from the ground after mechanically shaking the branches. The study revealed a decrease in the level of N, P, K, S, Cu and Zn during the development of the rubber tree's leaf. In contrast, during the same period the levels of Ca, Mg, B, Fe and Mn increased. The redistribution for N, P, K and Cu was higher and the relative order of macronutrient and micronutrient levels in the leaves were respectively: N>K>Ca>Mg≥S>P and Mn>Fe>Zn>B>Cu.