Improving biomass production and saccharification in Brachypodium distachyon through overexpression of a sucrose-phosphate synthase from sugarcane

The substitution of fossil by renewable energy sources is a major strategy in reducing CO2 emission and mitigating climate change. In the transport sector, which is still mainly dependent on liquid fuels, the production of second generation ethanol from lignocellulosic feedstock is a promising strategy to substitute fossil fuels. The main prerequisites on designated crops for increased biomass production are high biomass yield and optimized saccharification for subsequent use in fermentation processes. We tried to address these traits by the overexpression of a sucrose-phosphate synthase gene (SoSPS) from sugarcane (Saccharum officinarum) in the model grass Brachypodium distachyon. The resulting transgenic B. distachyon lines not only revealed increased plant height at early growth stages but also higher biomass yield from fully senesced plants, which was increased up to 52 % compared to wild-type. Additionally, we determined higher sucrose content in senesced leaf biomass from the transgenic lines, which correlated with improved biomass saccharification after conventional thermo-chemical pretreatment and enzymatic hydrolysis. Combining increased biomass production and saccharification efficiency in the generated B. distachyon SoSPS overexpression lines, we obtained a maximum of 74 % increase in glucose release per plant compared to wild-type. Therefore, we consider SoSPS overexpression as a promising approach in molecular breeding of energy crops for optimizing yields of biomass and its utilization in second generation biofuel production

Nutrient Concentrations and Uptakes in Giant Reed (Arundo donax L.) as Affected by Harvest Time and Frequency

The underlying aim of biomass crops is to combine high yields and low nutrient contents. Delayed harvests of perennial grasses can reduce nutrient concentrations, while higher levels are generally observed at early harvests. However, depending on the supply chain and the conversion technology, harvesting before senescence could be viable, leading to multiple harvesting, improved feedstock digestibility, and wet biomass storage. In this study, the influence of harvest time and frequency of giant reed (Arundo donax L.) was assessed on aboveground nitrogen, phosphorus, and potassium concentrations, removal, and nutrient use efficiency. In order to evaluate the effects of different cutting regimes, three single harvest (SH) and six double harvest systems (DH) were compared. Nutrient concentrations declined over the season from 10.3 to 2.5 gN kg−1, from 1.8 to 0.8 gP kg−1, and from 30.0 to 8.2 gK kg−1. Overall, DH led to higher nutrient concentrations than SH. Biomass at second cut tended to be richer in nutrients when harvested in autumn compared with winter, and when first cuts were delayed. Nutrient removal was markedly higher in DH for all the elements considered (on average, 196 kgN, 43 kgP, 530 kgK ha−1 in DH, 111 kgN, 29 kgP, 297 kg Kha−1 in SH). In DH systems, nitrogen and potassium use efficiencies were nearly halved compared with single late cuts, while phosphorus use efficiency decreased by about 30 %. The high nutrient removal rates of double-cut management suggest that it may be not sustainable, unless nutrient cycles are closed and nitrogen losses are evaluated