Mining saltmarsh sediment microbes for enzymes to degrade recalcitrant biomass

The recalcitrance of biomass represents a major bottleneck for the efficient production of fermentable sugars from biomass. Cellulase cocktails are often only able to release 75-80% of the potential sugars from biomass and this adds to the overall costs of lignocellulosic processing. The high amounts of fresh water used in biomass processing also adds to the overall costs and environmental footprint of this process. A more sustainable approach could be the use of seawater during the process, saving the valuable fresh water for human consumption and agriculture. For such replacement to be viable, there is a need to identify salt tolerant lignocellulose-degrading enzymes. We have been prospecting for enzymes from the marine environment that attack the more recalcitrant components of lignocellulosic biomass. To achieve these ends, we have carried out selective culture enrichments using highly degraded biomass and inoculum taken from a saltmarsh. Saltmarshes are highly productive ecosystems, where most of the biomass is provided by land plants and is therefore rich in lignocellulose. Lignocellulose forms the major source of biomass to feed the large communities of heterotrophic organisms living in saltmarshes, which are likely to contain a range of microbial species specialised for the degradation of lignocellulosic biomass. We took biomass from the saltmarsh grass Spartina anglica that had been previously degraded by microbes over a 10-week period, losing 70% of its content in the process. This recalcitrant biomass was then used as the sole carbon source in a shake-flask culture inoculated with saltmarsh sediment. Cultures were grown for 8 weeks and then analysed using meta-omic approaches. Meta-genomics were used to investigate the microbial community present in the final recalcitrant biomass, while combined meta-proteomics and meta-transcriptomics were used to identify putative CAZymes (Carbohydrate active enzymes). Candidate enzymes have been cloned, heterologous expressed in E. coli and characterized according to their salt tolerance

Controlling <i>In Planta</i> Gold Nanoparticle Synthesis and Size for Catalysis

Gold nanoparticles (Au-NPs) are used as catalysts for a diverse range of industrial applications. Currently, Au-NPs are synthesized chemically, but studies have shown that plants fed Au deposit, this element naturally as NPs within their tissues. The resulting plant material can be used to make biomass-derived catalysts. In vitro studies have shown that the addition of specific, short (∼10 amino acid) peptide/s to solutions can be used to control the NP size and shape, factors that can be used to optimize catalysts for different processes. Introducing these peptides into the model plant species, Arabidopsis thaliana (Arabidopsis), allows us to regulate the diameter of nanoparticles within the plant itself, consequently influencing the catalytic performance in the resulting pyrolyzed biomass. Furthermore, we show that overexpressing the copper and gold COPPER TRANSPORTER 2 (COPT2) in Arabidopsi sincreases the uptake of these metals. Adding value to the Au-rich biomass offers the potential to make plant-based remediation and stabilization of mine wastes financially feasible. Thus, this study represents a significant step toward engineering plants for the sustainable recovery of finite and valuable elements from our environment