Effect of arsenic speciation on growth, physiology, and bioethanol yield in two Miscanthus × giganteus genotypes

Miscanthus × giganteus, a major energy crop, is also considered for phytoremediation, yet its response to arsenic (As) remains underexplored. This pilot study assessed the tolerance of two morphologically distinct genotypes, 'Illinois' and 'D-116,' to soil contamination (10, 50, 100 mg kg^-1) with As(III), As(V), and dimethyloarsenic acid (DMA). We evaluated biometric traits, uptake of As and mineral nutrients (Ca, Mg, K, Na), photosynthetic performance (gas exchange, chlorophyll fluorescence and content), electrolyte leakage, and bioethanol production. 'Illinois' showed more evident physiological and biochemical responses, with As accumulation in shoots reaching up to 40 mg kg^-1, predominantly as DMA and other organic forms. Arsenic stress induced membrane dysfunction and disturbed ion homeostasis, but adaptive mechanisms mitigated growth reduction. Despite As accumulation, biomass remained a suitable substrate for bioethanol production via simultaneous saccharification and fermentation (SSF) technology. Ethanol yields were stable across treatments, with some combinations of As form × concentration increased raw yield to 41 g L^-1. Importantly, distillation reduced As levels in ethanol below detection threshold (<0.003 μg L^-1). This work provides the first integrative assessment of Miscanthus under arsenic stress, combining physiological traits, elemental and As speciation data, and fermentation outcomes. Our results demonstrate that M. × giganteus possesses considerable tolerance to As and retains dual utility for phytoremediation and bioenergy. Its perennial growth habit and high biomass yield highlight its potential for sustainable use on contaminated lands.