New Amylase Inhibitor Present in Corn Seeds Active In Vitro Against Amylase from Fusarium verticillioides

Implication of pre-drying steps with natural fumonisin contamination levels in freshly harvested corn

Maize quality regarding fumonisin contamination of 390 freshly harvested samples used by maize processing industries in the Northern region of Parana State, Brazil (2003 crop) was evaluated and correlated to the time elapsed from harvesting to the pre-drying step. Sampling was carried out at three points of the maize production chain, immediately after harvesting (n=100), at the industry delivery posts (n=200) and before the drying process (n=90). Fumonisin B1 (FB1) was detected in all the samples from the three points of the maize production chain. FB1 levels ranged from 0.11 to 12.68 µg/g (mean 1.81±2.12 µg/g) in the field samples, 0.10 to 11.83 µg/g (mean 1.83±1.75 µg/g) in the reception samples and from 0.02 to 10.98 µg/g (mean 2.31±2.38 µg/g) in the pre-drying samples. FB2 levels ranged from 0.01 to 5.26 µg/g (mean 0.84±0.94 µg/g) in the field samples, from 0.02 to 5.25 µg/g (mean 0.74±0.69 µg/g) in the reception samples and from 0.07 to 7.89 µg/g (mean 1.25±1.29 µg/g) in the pre-drying samples. Although there was no significant difference in mean fumonisin levels among the field, reception and pre-drying samples by the Tukey multiple comparison test (P<0.05), there was a positive correlation (P<0.05) between fumonisin levels and the time elapsed (p=0.95) from harvesting to the pre-drying step. Therefore reduction in the harvest/drying interval would be essential to assure product quality and safety and minimise potential health hazards.

Trends of fumonisin contamination and animal intoxication through monitoring 1991 to 1997 corn crop in the State of Paraná, Brazil

Eleven feed samples associated with six animal (horse and poultry) intoxication outbreaks (1991) in the state of Paraná, Brazil, were evaluated for fungal and fumonisin contamination. In order to estimate the trend of livestock intoxication, fumonisin contamination was monitored in corn produced both at the commercial level (1991, 1995 crop), and in an experimental field at a local Agronomy Institute (1997 crop). The total mould count in the feed samples ranged from 2.9 x 10(3) to 1.9 x 10(7) CFU/g, with Fusarium verticillioides as the predominant species, at a high count of 2.4 x 10(4)-6.5 x 10(5) CFU/g. Fumonisins (FB1 + FB2) were detected in all corn-based feed samples at levels ranging from 2.89 to 14.54 microg/g. All 27 Northern corn samples (1991 crop) were contaminated with fumonisins at levels ranging from 2.32 to 16.64 microg/g. Twenty-six (96.3%) out of 27 corn samples from the Central-Southern region (1995 crop) were positive for fumonisins (FB1+FB2), with the range of 0.07-3.66 microg/g, while all 37 Northern samples (1995 crop) were contaminated with fumonisins ranging from 0.57 to 9.97 microg/g. Twenty-one out of 37 corn samples from the Northern region (1997 crop) were positive for fumonisins, but at low level (range of 0.05-2.67 microg/g). The results showed a decreasing trend in fumonisin contamination over the years. Nowadays animal intoxication outbreaks rarely occur in this State, as both animal producers and feed industries have become conscious about monitoring of corn and other raw materials at the quality control level.

Characterization of a Hydrophobic Amylase Inhibitor from Corn (Zea mays) Seeds with Activity Against Amylase from Fusarium verticillioides

ABSTRACT A hydrophobic 19.7-kDa amylase inhibitor (AI) was purified from corn kernels by 95% ethanol extraction and anionic exchange chromatography. The AI has an isoelectric point of 3.6 and was very stable at different pH values and high temperatures, maintaining 47.6% activity after heating to 94 degrees C for 60 min. Amino acid analysis indicated high valine, leucine, glycine, alanine, and glutamic acid/glutamine content, and especially high valine content (41.2 mol%). This inhibitor is not a glycoprotein. It required 30-min preincubation to maximize complex enzyme-inhibitor formation when the amylase from Fusarium verticillioides was tested. The optimal pH of interaction was 6.5. It showed broad-spectrum activity including the following amylases: human saliva, porcine pancreas, F. verticillioides, as well as those from some insects of agricultural importance (Acanthoscelides obtectus, Zabrotes subfasciatus, Sitophilus zeamais, and Prostephanus truncatus). This novel hydrophobic protein not only inhibited the amylase from F. verticillioides but also decreased the conidia germination. Thus, this protein represents an approach to decrease the production of fumonisin in corn, either by using it as a molecular marker to detect fungal resistance or through genetic engineering.