A spectrophotometric method for quantitative determination of xylose in fermentation medium
Dave C. Swalm School of Chemical Engineering, Mississippi State University, Mississippi, MS 39762, USABiomass and Bioenergy (Impact Factor: 3.39). 04/2011; 35(7):2814. DOI: 10.1016/j.biombioe.2011.03.006
Monitoring the consumption of sugars during fermentation is a key to optimizing product formation and maintaining a healthy environment for microorganisms. Diffi-culty arises in the availability of a rapid, inexpensive and sensitive method for the detection of sugars because fermentation media are a complex mix of nutrients, cell debris, waste and target products. A method involving reaction-based UVeVis spectro-photometry for the quantitative determination of xylose as the target sugar was devel-oped. Factors affecting xylose concentration measurements such as hydrochloric acid concentration, heating time and the amount of Fe 3þ catalyst were investigated. A continuous scan revealed the working wavelength to be 671 nm. The effect of other components in the fermentation broth was found to be negligible. Absorbance shows a linear relationship with xylose concentration within a range of 0.1e0.5 g/L. Xylose concentrations from fermentation samples obtained at specific time intervals (0e168 h) were determined with the method and compared with YSI 2700, an enzyme electrode, HPLC-ELSD method, currently a common technique for measuring xylose and GC aldo-nonitrile sugar derivatization method. Dilution is necessary for comparable xylose concentrations with YSI 2700 and HPLC-ELSD. Xylose concentration measurements obtained with the UVeVis spectrophotometric method although quantitatively compa-rable to HPLC-ELSD xylose measurements were easily and conveniently obtained compared to YSI 2700, HPLC-ELSD and GC derivatization methods.
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ABSTRACT: This study demonstrated a new method for analyzing five-carbon sugars in biomass hydrolysate by headspace gas chromatography (HS-GC). The proposed method is based on the reaction of five-carbon sugars with sulfuric acid, in which five-carbon sugars are converted to furfural that is measured with full evaporation headspace gas chromatography (FE-HSGC) using a flame ionization detector (FID). The experimental results showed that the complete conversion of five-carbon sugars to furfural can be achieved at 70 °C within 5 min, with a H2SO4 concentration of 15 mol/L. Moreover, it can be seen that the measurement precision (RSD ≤ 0.72%) and accuracy (recovery = 99.3 ± 1.9%) are very good. The operating procedure is simple, and the testing time is short. In addition, the proposed method does not need organic reagents. All of these demonstrate that the peoposed method is a rapid, reliable, and environmentally friendly method that is quite suitable for the analysis of five-carbon sugars in the hydrolysate during the process of lignocellulosic biomass conversion.
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ABSTRACT: Development of a novel method for the quantification of lovastatin is an interesting problem in the analytical field. In the literature, many reports use spectrophotometric method for the quantification of lovastatin. However, the analysis of fermentation broth containing lovastatin appears to be inaccurate using spectrophotometric method. Hence, the estimation of lovastatin produced by Monascus purpureus and pure lovastatin was attempted by UV-visible spectrophotometer as well as HPLC. It was observed that the analogues and/or intermediates of lovastatin synthesized in the fermentation broth and the products of fermentation caused superimposition effect on the absorption spectrum. Phosphate is a medium constituent for the production of lovastatin by the organism which contributed significantly to the superimposition of absorption spectrum. On the other hand, HPLC analysis consistently gave reliable results for the estimation of lovastatin under all the experimental conditions studied.
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ABSTRACT: Ethanol production from sugarcane bagasse requires a pretreatment step to disrupt the cellulose-hemicellulose-lignin complex and to increase biomass digestibility, thus allowing the obtaining of high yields of fermentable sugars for the subsequent fermentation. Hydrothermal and lime pretreatments have emerged as effective methods in preparing the lignocellulosic biomass for bioconversion. These pretreatments are advantageous because they can be performed under mild temperature and pressure conditions, resulting in less sugar degradation compared with other pretreatments, and also are cost-effective and environmentally sustainable. In this study, we evaluated the effect of these pretreatments on the efficiency of enzymatic hydrolysis of raw sugarcane bagasse obtained directly from mill without prior screening. In addition, we evaluated the structure and composition modifications of this bagasse after lime and hydrothermal pretreatments. The highest cellulose hydrolysis rate (70 % digestion) was obtained for raw sugarcane bagasse pretreated with lime [0.1 g Ca(OH) 2 /g raw] for 60 min at 120 °C compared with hydrothermally pretreated bagasse (21 % digestion) under the same time and temperature conditions. Chemical composition analyses showed that the lime pretreatment of bagasse promoted high solubilization of lignin (30 %) and hemicellulose (5 %) accompanied by a cellulose accumulation (11 %). Analysis of pretreated bagasse structure revealed that lime pretreatment caused considerable damage to the bagasse fibers, including rupture of the cell wall, exposing the cellulose-rich areas to enzymatic action. We showed that lime pretreatment is effective in improving enzymatic digestibility of raw sugarcane bagasse, even at low lime loading and over a short pretreatment period. It was also demonstrated that this pretreatment caused alterations in the structure and composition of raw bagasse, which had a pronounced effect on the enzymes accessibility to the substrate, resulting in an increase of cellulose hydrolysis rate. These results indicate that the use of raw sugarcane bagasse (without prior screening) pretreated with lime (cheaper and environmentally friendly reagent) may represent a cost reduction in the cellulosic ethanol production.
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