[Zeolite catalysis in conversion of cellulosics]

To transform biomass into fermentable substrate for yeast, we are using zeolites instead of enzymes to catalyze the two bottleneck reactions in biomass conversion, xylose isomerization and ceuobiose hydrolysis. The experimental results on these reactions carried out over various zeolites and other catalysts are presented herein. The advantages and disadvantages of using these catalysts over enzymes are also discussed. Heterogeneous solid catalysts other than zeolites has been employed for cellobiose-to-glucose hydrolysis. The size and shape selectivity that makes zeoutes unique for some reactions can add diffusional hindrance. We have spent some time screening various known solid acidic catalysts. We report that a class of cationic ion exchange resins in the acidified form (e.g. Amberlite) has worked well as an acidic catalyst in hydrolyzing cellobiose to glucose. Our experimental results, together with those obtained from a homogeneous acid catalyst (e.g. sulfuric acid) for comparison are provided. Having succeeded in finding an alternative solid acid catalyst for hydrolysis, we explored other solid resin or other homogeneous but non-enzyme catalyst to carry out the xylose-to-xylulose isomerization. A fairly extensive search has been made. We explored the use of sodium aluminates in the homogeneous phase isomerization of glucose to fructose and obtained a very high conversion of glucose to fructose with the final mixture containing 85% of fructose instead of the common 45%. Fructose apparently complexes with aluminates, and its equilibrium concentration is shifted to considerably higher values than permitted by simple glucose/fructose equilibrium. We have recently found a number of catalysts capable of promoting isomerization between aldoses and ketoses. One solid resin, known as polyvinyl pyridine (PVP), is able to convert xylose to xylulose at a pH below 7. Our usage of alternative isomerization catalysts, including PVP, are described

Production of renewable polymers from crop plants

Plants produce a range of biopolymers for purposes such as maintenance of structural integrity, carbon storage, and defense against pathogens and desiccation. Several of these natural polymers are used by humans as food and materials, and increasingly as an energy carrier. In this review, we focus on plant biopolymers that are used as materials in bulk applications, such as plastics and elastomers, in the context of depleting resources and climate change, and consider technical and scientific bottlenecks in the production of novel or improved materials in transgenic or alternative crop plants. The biopolymers discussed are natural rubber and several polymers that are not naturally produced in plants, such as polyhydroxyalkanoates, fibrous proteins and poly-amino acids. In addition, monomers or precursors for the chemical synthesis of biopolymers, such as 4-hydroxybenzoate, itaconic acid, fructose and sorbitol, are discussed briefl