Maillard reaction in Natural Rubber (NR) latex was investigated by treating fresh NR latex with glutaraldehyde (C5H8O2) in amounts of 0, 50, 100, and 200 mmol/kg of latex. Protein cross-linking in fresh NR latex and solid NR was confirmed by using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and attenuated total reflection infrared (ATR-IR) spectroscopy, respectively. It was found that degree of protein cross-linking in NR increased with increasing C5H8O2concentration. Physical properties of untreated and treated NR substances in terms of gel content, initial Wallace plasticity (P0), plasticity retention index (PRI), Mooney viscosity, and tensile strength were carefully explored. Results clearly showed that the Maillard cross-linking of proteins had remarkable effect on bulk NR properties, that is, solvent resistance, hardness, resistance to oxidation, rheological behavior, and resistance to stretching out.

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Pretreatment is a prerequisite step for increasing the enzymatic digestibility of agricultural residues for conversion to fuels and chemicals in biorefineries. In this study, a sequential acid and alkaline process was developed for pretreatment of rice straw for ethanol fermentation. Effects of key parameters in acid pretreatment were studied using a full factorial design model, which showed the higher influence of time compared to acid concentration and temperature on reducing sugar yields. The combined sequential process involved an initial hemicellulose solubilization by dilute acid using 1% (w/v) H2SO4 at 125 °C for 10 min, followed by alkaline delignification using 1.25% NaOH at 90 °C for 10 min. Under these conditions, a glucose recovery yield of 70.9% from saccharification of the cellulose enriched fraction was obtained with 2-to 4-fold savings in chemical usage as compared with single-step processes. Scanning electron microscopy revealed modification of biomass micro-structure and increases in reactive surface area. Simultaneous saccharification and fermentation of the solid residues by Saccharomyces cerevisiae, using 25 FPU/g Accellerase ® 1500, led to a final ethanol concentration of 21.0 g/L with the productivity of 0.27 g/L/h, equivalent to 84.6% theoretical yield. The results indicate the potential of the sequential process for increasing pretreatment efficiency and allowing stepwise separation of lignocellulose components for multi-product biorefineries.

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