ABSTRACT
The use of lipids obtained from microalgae biomass has been described as a promising alternative for production of biodiesel to replace petro-diesel. It involves steps such as the cultivation of microalgae, biomass harvesting, extraction and transesterification of lipids. The purpose of the present study was to compare different methods of extracting total lipids. These methods were tested in biomass of Chlorella vulgaris with the solvents ethanol, hexane and a mixture of chloroform:methanol in ratios 1:2 and 2:1. The solvents were associated with other mechanisms of cell disruption such as use of a Potter homogenizer and ultrasound treatment. The percentage of triglycerides in the total lipids was determinated by the glycerol-3-phosphate oxidase-p-chlorophenol method (triglycerides monoreagent K117; Bioclin). Among the tested methods, the mixture of chloroform:methanol (2:1) assisted by ultrasound was most efficient, extracting an average of 19% of total lipids, of which 55% were triglycerides. The gas chromatographic analysis did not show differences in methyl ester profiles of oils extracted under the different methods.
Subject(s)
Biomass , Chemical Fractionation/methods , Chlorella vulgaris/chemistry , Lipids/isolation & purification , Lipids/chemistry , Triglycerides/analysisABSTRACT
The process of biodiesel production by the hydroesterification route that is proposed here involves a first step consisting of triacylglyceride hydrolysis catalyzed by lipase from Thermomyces lanuginosus (TL 100L) to generate free fatty acids (FFAs). This step is followed by esterification of the FFAs with alcohol, catalyzed by niobic acid in pellets or without a catalyst. The best result for the enzyme-catalyzed hydrolysis was obtained under reaction conditions of 50% (v/v) soybean oil and 2.3% (v/v) lipase (25 U/mL of reaction medium) in distilled water and at 60°C; an 89% conversion rate to FFAs was obtained after 48 hours of reaction. For the esterification reaction, the best result was with an FFA/methanol molar ratio of 1:3, niobic acid catalyst at a concentration of 20% (w/w FFA), and 200°C, which yielded 92% conversion of FFAs to soy methyl esters after 1 hour of reaction. This study is exceptional because both the hydrolysis and the esterification use a simple reaction medium with high substrate concentrations.
ABSTRACT
To compare the performance of human papillomavirus DNA tests (samples collected by a healthcare professional and self-collected) and liquid-based cytology with conventional cytology in the detection of cervix uteri cancer and its precursor lesions. A cross-sectional study was carried out in 1777 women living in poor communities in Rio de Janeiro State, Brazil. Eligibility criteria included ages 25-59 years and not having had a Papanicolau test within at least 3 years prior to the study. Cytology (conventional or liquid-based) and human papillomavirus DNA (collected by a healthcare professional or self-collected) tests were performed using samples collected in a single visit. Women with abnormalities in at least one test and a systematic sample of 70 women with negative test results were referred to a colposcopic examination. Test readings were double-masked, and the outcome of interest was high-grade squamous intraepithelial lesion or worse. The pathology report was used as the gold standard. The prevalence of high-grade squamous intraepithelial lesion or worse was 2.0%. Human papillomavirus DNA test collected by a health professional alone or combined with conventional cytology had the highest sensitivity (91.4 and 97.1%, respectively). The highest specificity was found for conventional cytology (91.6%) and for a human papillomavirus DNA test collected by a healthcare professional (90.2%). On the basis of only test performance, the use of human papillomavirus DNA tests, alone or combined with cytology, would seem to be recommended. Its population-wide implementation, however, is conditional on a cost-effectiveness analysis.
