To build an energy and material secure future, a next generation of renewable fuels and bio-based chemicals produced from lignocellulosic biomass is required. Consolidated bioprocessing (CBP), which integrates enzyme production, saccharification and fermentation into a single process, is a promising strategy for effective production of bio-based materials. As a key technology for the development of recombinant cellulolytic microbial strains, cell surface engineering, which enables the display through genetic engineering of various types of functional proteins on microbial cell surfaces without loss of their function, is a promising tool reducing the requirement for cellulase addition, as cellulases can be displayed on the microbial cell surface. Regardless of the process used for the biomass hydrolysis, CBP-enabling microorganisms encounter a variety of toxic compounds released during biomass pretreatment that inhibit microbial growth and ethanol yield. Systems biology approaches including transcriptomics and metabolomics have been recently exploited to gain insight into the molecular and genetic traits involved in tolerance and adaptation to the fermentation inhibitors. A combination of a cell surface displayed enzyme system and an intracellular metabolic engineering system is a very effective approach to develop cells with novel fermentation ability for industrial applications.

We Enzyme Research Team, RIKEN, investigate biopolymer synthesis from plant and marine biomass using enzyme, bacteria and plant as biocatalysts. Here, our recent updates on biosyntheses and material design of polyhydroxyalkanoate (PHA) are summarized. Also, future perspectives on biopolymer synthesis via enzymatic reactions of plant and/or cyanobacteria using carbon dioxide as carbon source are introduced at the end of this short review.

The logic and point for wood biomass utilization were surveyed, and then 3 kinds of pretreatment method developed by our group were introduced. In these methods, the direct saccharification is an efficient separation method by which cellulose fraction is saccharified with remaining lignin fraction as a solid. Next, we proposed a new method for converting thermo-chemically lignin fraction into valuable chemicals as a useful utilization of lignin. It was shown that only 3 organic acids (formic, acetic, and succinic acids) were successfully obtained in total yield of 45 wt% by oxidative decomposition of lignin for several minutes at 200°C in the presence of H₂O₂. Finally, a new method for direct conversion of wood biomass to chemicals was shown. The method was 2 step thermo-chemical processes of liquid phase oxidation by hydrogen peroxide and hydrothermal decomposition. Several kinds of valuable chemicals such as furfural and HMF were successfully recovered selectively in high yield by the oxidation with 0.5% H₂O₂ at 200°C and hydrothermal decomposition at 240°C. Thus, it was clearly shown that thermo-chemical conversion of wood biomass will be an attractive way to produce valuable chemicals.

This account deals with developing trend of biomass plastics based on plant oils. Network polymers were obtained from epoxidized soybean and linseed oils by ring-opening polymerization or curing with acid anhydrides. The oil polymer composites were synthesized using cellulose fibers as filler, and their physical and thermal properties were improved in comparison with those of the oil polymers. A bio-based coating for roofs was developed from epoxidized plant oil-modified acrylic polyol. Bio-based polyols for polyurethane production were prepared using castor oil as starting material. Branched poly(lactic acid) bearing a castor oil core was used for preparation of the polyurethane form. It also acted as plasticizer and nucleating agent for biopolyesters such as poly(lactic acid) and poly(3-hydroxyalkanoate)s.

Recently, various bio-based plastics are developed from renewable resources. However, there are still many problems as physical and thermal properties, processability, productivity, utilization of edible materials as carbon sources for practical use of them. We report at first the approach of microbial synthesis of polyhydroxyalkanoates that are bio-based and biodegradable polyesters by using not only from pure plant oils but also from non-edible oils and waste edible oils. Furthermore, the synthesis and characterization of xylan ester derivatives and their application as a nucleating agent for poly(lactic acid) are described. At the last part, polycondensation of caffeic acid, that is a plant-derived aromatic compound, was performed with the aim of developing novel heat-resistant bio-based plastics.