Optimization studies on laccase activity of Proteus mirabilis isolated from treatment sludge of textile industry factories : Optimization of laccase activity of Proteus mirabilis.

Laccase is an exothermic enzyme with copper in its structure and has an important role in biodegradation by providing oxidation of phenolic compounds and aromatic amines and decomposing lignin. The aim of this study is to reach maximum laccase enzyme activity with minimum cost and energy through optimization studies of Proteusmirabilis isolated from treatment sludge of a textile factory. In order to increase the laccase enzyme activities of the isolates, medium and culture conditions were optimized with the study of carbon (Glucose, Fructose, Sodium Acetate, Carboxymethylcellulose, Xylose) and nitrogen sources (Potassium nitrate, Yeast Extract, Peptone From Soybean, Bacteriological Peptone), incubation time, pH, temperature and Copper(II) sulfate concentration then according to the results obtained. Response Surface Method (RSM) was performed on six different variables with three level. According to the data obtained from the RSM, the maximum laccase enzyme activity is reached at pH 7.77, temperature 30.03oC, 0.5 g/L CuSO4, 0.5 g/L fructose and 0.082 g/L yeast extract conditions. After all, the laccase activity increased 2.7 times. As a result, laccase activity of P. mirabilis can be increased by optimization studies. The information obtained as a result of the literature studies is that the laccase enzymes produced in laboratory and industrial scale are costly and their amounts are low. This study is important in terms of obtaining more laccase activity from P.mirabilis with less cost and energy.

Determination of optimization parameters based on the Box-Behnken design for cloud point extraction of quinoline yellow using Brij 58 and application of this method to real samples.

Quinoline yellow (E104) dye is a food additive and generally used in cosmetics and drugs. In this work, polyethylene glycol hexa decyl ether (Brij 58) was used for the spectrophotometric determination of quinoline yellow (QY) in food and drug samples after cloud point extraction (CPE). Some parameters such as extraction temperature and time, pH, centrifuge speed, Brij 58 (surfactant) concentration, and Na2SO4 concentration were optimized using Box-Behnken design. The limit of detection (LOD) of this method was 0.0019 µg mL-1 for QY while the relative standard deviation (RSD) at low concentration levels (0.03 µg mL-1) was 1.32% (n = 5). Findings indicated that, this novel CPE method can be used quickly for the reproducible, selective and sensitive determination of QY dye in ordinary analysis.