Dilute acid pretreatment of lignocellulosic biomass at higher temperatures (>160 °C) solubilizes/removes hemicelluloses (xylan, arabinan, mannan, galactan) and acidsoluble lignin (ASL), but, it does not remove acid-insoluble lignin (AIL). During acid pretreatment, the condensation and redeposition of coalesced lignin over cellulose fibers reduces the access of cellulose to cellulases. For higher delignification, various multistage pretreatments are available, however, all these are energy/chemical intensive methods. Therefore, an effective pretreatment which provides increased cellulose accessibility by enhanced removal of hemicelluloses and lignin in a single-step would be preferred. Our investigation reports a novel assisted single-step acid pretreatment (ASAP) process for enhanced delignification of biomass under acidic conditions. Pretreatment of rice straw (particle size of 20 mm) with H 2 SO 4 (0.75% v/v) + boric acid (1% w/v) + glycerol (0.5% v/v) (solid/liquid (S/L), 1:5) at 150 °C for 20 min removed hemicelluloses completely, 44% of the lignin, and ∼48.5% of the silica leaving a solid consisting of 69 ± 1.5% glucan, 0.7 ± 0.06% ASL, 20 ± 2.0% AIL, and 12 ± 1.5% silica. The C/L (cellulose/ lignin) ratio of solids resulted from ASAP was found to be > 3.00, while it was < 2.00 for acid only and untreated solids. Enzymatic hydrolysis of ASAP treated biomass with enzyme loadings of 20 FPU g −1 at 15% (w/v) solids concentration gave about 72% glucan conversion to glucose. This amount of glucose was around 2.6 times higher than obtained with enzymatic hydrolysis of acid-only-pretreated solids and 4.2 times higher than untreated rice straw (control). Therefore, the assisted-acid pretreatment dramatically enhanced delignification of rice straw and thereby glucan-to-glucose conversion.

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This paper reports biotransformation of (L)-citronellal to (L)-citronellol using free and immobilized cells ofMonoterpenes are widely distributed in nature and find extensive applications in the flavor and fragrance industry. Their simple structures make them ideal targets for microbial biotransformations to yield several commercially important products (Werf et al. 1997). Citronellal (3,7-Dimethyl-6-octanal), a monoterpene which occurs in the L or D form, bears distinct odor characteristics and also occurs as a constituent of essential oils in Eucalyptus citriodora (Betts, 2000). Citronellal can be further hydrogenated to produce citronellol (3,, which is a commercially important product due to the peculiar rose -like odor characteristics of the product (Guenther, 1950).The chemical synthesis of citronellol has *Corresponding Author been reported via hydrogenation of citronellal using polymer-stabilized noble metal colloids (Weiyong et al. 2000). It would be interesting to generate (L)-citronellol via bioconversion from (L)-citronellal as (L)-citronellol generated via biotransformation is labeled as a 'natural' product and commands higher value in the market than it's chemically produced counterpart. The biotransformation of other optical isomer i.e. (D)-citronellal to (D)-citronellol using Pseudomonas aeruginosa (Joglekar and Dhavalikar, 1969) and Saccharomyces cerevisiae (Ward and Young, 1991;Chatterjee et al. 1999) have been reported. A patented report using Candida reukaufii mediated (L)-citronellal biotransformation to (L)-citronellol with 80% optical purity is also available (Takasago, 1974). However, information on the biotransformation of (L)-citronellal to (L)-citronellol remains limited. The optimization of process parameters remains a challenging task due to several limitations posed by monoterpenes such as toxicity and volatility, by-product formation, immiscibility and low yields of the product (Krasnobajew, 1984 91utilis mediated biotransformation of benzaldehyde to Lphenylacetylcarbinol, the toxic effects of the substrate on immobilization of the yeast cells were minimized (Oliver et al. 1999). In the present work, the optimal conditions for R. minuta growth and its application in biotransformation of (L)-citronellal to (L)-citronellol by free and immobilized cells is reported. The reuse of immobilized cells is presented in this work. The biotransformation reaction using R. minuta cells is schematically presented in Figure 1. The suitable culture conditions such as pH, temperature and agitation were studied to maximize the product concentration. Immobilization was examined as a means to offset substrate toxicity. MATERIALS AND METHODS Microorganism and cultural conditionsStrain of Rhodotorula minuta (NCIM 3359) was obtained from National Collection of Industrial Microorganisms, NCL, India and maintained on potato/dextrose/agar slants (pH 5.5) at 4ºC. For cultivation in liquid media, growth from slants was inoculated in 250 ml sterile PDB in 500 ml Erlenmeyer flasks and incubated at 27ºC, pH 5.5...