Post-harvest modifications and implications for recovery of bioenergy or biorenewables

Optimized harvesting, storage and processing of plant biomass are essential for the efficient recovery of bioenergy and other biorenewables. The characterisation of traits linked to post-harvest deterioration of biomass will provide targets for plant breeding and information for the development and optimization of technologies to minimise the losses which occur via respiration, tissue damage, senescence and microbial degradation. Respiration and microbial activity will potentially result in carbon losses while senescence ultimately results in hydrolysis of carbohydrates, nucleic acids and protein polymers and cell wall degradation. Wounding typically results in increased polyphenol oxidase (PPO) and peroxidase activity. These enzymes are present in Miscanthus and Lolium leaf tissues. Polyphenol oxidase and peroxidase activities result in the production of quinones which readily bind with proteins and other plant components with nucleolphilic sites such as cell-wall phenolics. The implications of these enzyme activities are an inactivation of plant hydrolytic enzymes, and a decreased degradability of cell walls and lipids. These changes may have adverse effects on biomass fermentation by preventing plant enzyme activity from increasing bioavailability and by making cell-walls less degradable. Alternatively, these properties may prevent carbon losses via respiration and microbial activity and may be of benefit for thermal conversion processes. This sub-programme involves biochemical and transcriptomic studies on post-harvest biomass. This data is also been related to senescence and enzyme activities, eg. for PPO/ peroxidase/ glycosidase. Changes in potential natural products, as detected by LC-MS are being characterised and linked to transcript analyses. The objective is to identify molecular markers and genes associated to QTL for post-harvest traits in biorenewable crops. Candidate genes and associated regulatory regions will be functionally tested in Miscanthus.