Production, partial purification, and characterization of a glucoamylase from Epicoccum nigrum

Starch processing industries use amylases, accounting for approximately 30% of the world's enzyme market. Previously, an amylase-producing strain of Epicoccum nigrumwas isolated from maize grains. Although E. nigrumamylase production is already reported in the literature, no published data on production optimization or characterization of the produced enzyme exists. The objectives of this work were to improve the amylase production by theE. nigrumPG 16 strain and to purify and characterize the produced enzyme. The E. nigrumPG 16 amylase production best conditions in submerged culture were: inoculum of 4% (v v-1) of a five-days-old stationary culture homogenate, agitation at 100 rpm, 25°C, natural light, 72 hours of incubation, starch as thecarbon source, and an initial medium pH of 7.0. A molecular exclusion chromatography profile has shown the production of only one amylase, which was partially purified with ammonium precipitation and dialysis. The enzyme optima pH and temperature are 6.0 and 50°C, respectively. The partially purified enzyme lostits activity when incubated for 30 min in temperatures above 40°C, presenting a T50of 46.25°C. The KMand Vmaxof the partially purified enzyme are 1.72 mg mL-1of starch and 0.15 mgmin-1of degraded starch, respectively. The ion Ca2+slightly activated the studied enzyme. The ions Cu2+, Zn2+, and Fe3+and the detergents SDS and Tween 80 acted as inhibitors of the studied enzyme. The partially purified enzyme released glucose from p-nitrophenyl α-D-glucopyranoside (p-NPG). Glucose was the enzyme's main product from starch hydrolysis, as evidenced by thin-layer chromatography. The E. nigrumPG 16 studied enzyme is a glucoamylase and represents an alternative for enzymatic starch hydrolysis.(AU)

The occurrence of aflatoxigenic Aspergillus spp. in dairy cattle feed in Southern Brazil

The presence of mycotoxins or related fungi in animal feed is a major problem for animal and human health. Silage and concentrated feed samples were collected from 21 dairy farms in the Western part of Paraná state in Southern Brazil. Water activity and pH of all samples were measured, and each sample was analyzed to check for the presence of aflatoxigenic Aspergillus. Water activity was observed to be lower in the concentrated feed samples. The pH was lower in the silage samples, indicating fermentation processes. Two silage samples and four concentrated feed samples were contaminated with Aspergillus spp. Seven isolates of Aspergillus spp. were obtained and their potential to produce aflatoxins was evaluated. Four of the isolates, two from the silage samples and two from the concentrated feed samples, produced the aflatoxins B1, B2, G1, and G2 in culture media. These isolates were identified as Aspergillus parasiticus and Aspergillus nomius. The presence of aflatoxigenic isolates of Aspergillus spp. in silage and concentrated feed samples is a matter of concern, because of the risk of aflatoxin production and contamination of the animal feed.(AU)

Occurrence of zearalenone in wheat- and corn-based products commercialized in the State of Paraná, Brazil

The productivity of wheat and corn crops depends on climatic conditions and resistance against phytopathogenic fungi such as those of the genus Fusarium. Some species of this genus produce zearalenone (ZEA), a mycotoxin with hyperestrogenic effects. The objective of this study was to investigate the presence of ZEA in samples of cracked wheat (n = 109), popcorn (n = 51) and corn grits (n = 50) commercialized in the State of Paraná, Brazil. Commercial samples of each crop were collected between September 2007 and June 2008 and analyzed by thin-layer chromatography. The method used for detection of the mycotoxin in wheat and corn derivatives presented a recovery rate of 94.5% and 99.5%, respectively, detection limit of 40 g.kg-1 and quantification limit of 55 g.kg-1. No contamination with ZEA was detected in cracked wheat samples. Among the corn derivatives, only one cracked corn sample was contaminated with ZEA (64 g.kg-1). Despite the low contamination observed, monitoring the occurrence of mycotoxins in foods is important to ensure safety.(AU)