Maize Kernel Hardness, Endosperm Zein Profiles, and Ethanol Production

Abstract

Maize (Zea mays L.) grain is an important feed- stock for the ethanol-producing industry. However, little is known about the optimum grain quality for optimizing ethanol yielding efficiencies. We specifically investigated the re-sponse of ethanol yields (L Mg−1) to kernel hardness, and itsphysiological determinant endosperm zein protein profiles, asaffected by genotype selection, field nitrogen (N) fertilization,and crop growth environment. We measured ethanol yield andrelated this to different kernel hardness indicators, kernel com-position, and zein profiles. We also described changes in fieldethanol yield (L ha−1), by taking into account the crop yield(Mg ha−1). Hard endosperm genotypes always yielded lessethanol than softer endosperm ones per grain mass(L Mg−1). Higher N fertilization rates increased kernel hard-ness and decreased ethanol yield (L Mg−1) on soft endospermdented genotypes but had no effect on hard endosperm ones.Ethanol yield was negatively correlated with kernel density,kernel protein concentration, and Z1 and Z2 zein fractions.Within Z2, 15 kDa β-zein explained the largest ethanol yieldvariation generated by genotypes, N fertilizations, and growth 29environments. However, and although these differences were 30 Q3as large as 10%, ethanol field yield (L ha 31 −1) was mainly drivenby crop yields (r 32 2 0.98) due to the large crop yield (Mg ha−1)differences observed across treatments. Together, our results 33helped describe the magnitude that changes in maize kernel 34hardness can have over ethanol yield, both through genotype 35selection or crop management. A particular Z2 zein protein 36rises as relevant for future genetic manipulations of maize 37ethanol yield determination.