Fumonisins in conventional and transgenic, insect-resistant maize intended for fuel ethanol production: implications for fermentation efficiency and DDGS co-product quality.

Erin L Bowers,Gary P Munkvold

doi:10.3390/toxins6092804

Abstract

Mycotoxins in maize grain intended for ethanol production are enriched in co-product dried distiller’s grains and solubles (DDGS) and may be detrimental to yeast in fermentation. This study was conducted to examine the magnitude of fumonisin enrichment in DDGS and to analyze the impacts of insect injury, Fusarium ear rot severity, and fumonisin contamination on final ethanol yield. Samples of naturally-contaminated grain (0 to 35 mg/kg fumonisins) from field trials conducted in 2008–2011 were fermented and DDGS collected and analyzed for fumonisin content. Ethanol yield (determined gravimetrically) was unaffected by fumonisins in the range occurring in this study, and was not correlated with insect injury or Fusarium ear rot severity. Ethanol production was unaffected in fumonisin B1-spiked grain with concentrations from 0 to 37 mg/kg. Bacillus thuringiensis (Bt) maize often has reduced fumonisins due to its protection from insect injury and subsequent fungal infection. DDGS derived from Bt and non-Bt maize averaged 2.04 mg/kg and 8.25 mg/kg fumonisins, respectively. Fumonisins were enriched by 3.0× for 50 out of 57 hybrid × insect infestation treatment combinations; those seven that differed were <3.0 (1.56 to 2.56×). This study supports the industry assumption of three-fold fumonisin enrichment in DDGS, with measurements traceable to individual samples. Under significant insect pest pressures, DDGS derived from Bt maize hybrids were consistently lower in fumonisins than DDGS derived from non-Bt hybrids.

Highlights

The maize ethanol industry continues to grow steadily in the United States, keeping in step with federal government directives for the inclusion of renewable fuels in the U.S fuel supply
Results were obtained by combining the dried distiller’s grains and solubles (DDGS) from four individual fermentations at each level of spike, and using these as one sample for HPLC determination of FB1
In addition to potential gains in ethanol productivity per unit land area, this study has shown that Bacillus thuringiensis (Bt) maize hybrids produce higher quality DDGS as compared with non-Bt DDGS, from the standpoint of fumonisin mycotoxin contamination

Summary

Introduction

The maize ethanol industry continues to grow steadily in the United States, keeping in step with federal government directives for the inclusion of renewable fuels in the U.S fuel supply. Policy Act of 2005 [1] and the Energy Independence and Security Act of 2007 [2] bolstered mandates for biofuel inclusion and directed that maize-based ethanol should constitute 57 billion liters (15 billion gallons) of the U.S fuel supply annually by the year 2015. As of 2013, 211 maize ethanol plants are operating in 28 states with a total production capacity of 55.65 billion L (14.7 billion gallons) annually [3]. Gasoline/ethanol blends continue to comprise 95% of the total fuel consumed in the United States, the majority of which is a blend of

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