Abstract The antibacterial secondary metabolites of the fungus Penicillium chrysogenum associated with the beetle Aspongopus chinensis were investigated through chromatographic fractionation methods of ethyl acetate extracts of the fungal cultures. Five compounds were isolated, and their structures were determined as emodin, 4-(methoxymethyl)benzoic acid, isoochracinic acid, secalonic acid D, and dicerandrol A using mass spectroscopy and nuclear magnetic resonance spectroscopic analyses. Emodin exhibited strong antimicrobial activity, especially against Staphylococcus aureus even when growing on cooked pork, with a minimal inhibitory concentration (MIC) of 6.3 μg/mL. Dimeric tetrahydroxanthones, such as secalonic acid D and dicerandrol A, also exhibited potent activity, with MIC values ranging from 9.5 to 28.5 μg/mL. In summary, P. chrysogenum was isolated as a symbiotic fungus of the beetle A. chinensis for the first time and this strain could generate antibacterial secondary metabolites, which could potently inhibit gram-positive bacteria growth in vitro.

In this study, exo-polygalacturonase (exo-PG) production from Aspergillus niger SW06 was optimized by central composition design and high amount of 21.51 units mL-1 could be achieved in optimizing growth conditions. Both gel filtration and ion exchange chromatography revealed a single exo-PG activity peak, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the purified protein showed a single band with a molecular mass of 66.2 kDa. The purified enzyme exhibited maximal activity in the presence of 1% citrus pectin at the temperature of 55 ºC and pH of 5.0. The enzyme was stable within the pH range of 3.0-5.0 and below 60 ºC. The Michaelis constant (Km) and maximum velocity (Vmax) of the enzyme was found to be 0.58 mg mL-1 and 20.66 μmol (mL min)-1, respectively. The thermostable and acidic nature for the activity of this exo-PG make it possible to have wide range of industrial applications.

RESUMO Penicillium janthinellum sw09, isolado do solo, produz quantidades significativas de uma pectinase extracelular que foi posteriormente caracterizada como exo-poligalacturonase (exo-PG). Ao otimizar as condições de crescimento, P. janthinellum sw09 produz quantidades elevadas de exo-PG (16,54 unidades/ml). A enzima impura foi purificada por cromatografia de filtração em gel e dois picos com atividade elevada de exo-PG (designados como PGI e PGII) foram revelados. Por análise em SDS-PAGE, PGII foi purificada utilizando uma coluna de DEAE-Sepharose FF, observou ser formada por uma única banda com uma massa molecular de 66,2 kDa. PGII purificada exibiu uma actividade máxima a uma temperatura de 45 °C e pH 5,0. Os perfis de estabilidade mostram que PGII é mais estável numa faixa de pH de 4,0-8,0 e abaixo de 60 ° C. O Km e Vmax para a enzima foi de 1,74 mg / ml e 18,08 μmol / (mL • min), respectivamente. Devido a esta caracterização enzimática, pectinase é um candidato atrativo para ser aplicado na degradação da pectina.

ABSTRACT A soil isolate, Penicillium janthinellum sw09 has been found to produce significant amounts of an extracellular pectinase subsequently characterized as exo-polygalacturonase (exo-PG). By optimizing growth conditions, P. janthinellum sw09 produced high amount of exo-PG (16.54 units/mL). The crude enzyme was purified by gel filtration chromatography and two exo-PG activity peaks (designated as PGI and PGII) were revealed. On SDS-PAGE analysis, purified PGII using DEAE-Sepharose FF column, was found to be a single band with a molecular mass of 66.2 kDa. The purified PGII exhibited maximal activity at the temperature of 45 oC and pH 5.0. The stability profiles show that PGII is more stable in the pH range of 4.0-8.0 and below 60 oC. The Km and Vmax for the enzyme was 1.74 mg/mL and 18.08 μmol/ (mL•min), respectively. Due to this enzymatic characterization, this pectinase is an attractive candidate for applications in degradation of pectin.