Abstract
Pseudomonas aeruginosa was repeatedly reported as powerful producer of rhamnolipid biosurfactants as well as producer of hydrolytic enzymes. In this study effects of four fermentation factors were evaluated using response surface methodology and experiments were performed in accordance with a four-factor and five-level central composite experimental design. Investigated factors were: fermentation temperature, time of fermentation, concentration of sunflower oil and concentration of Tween? 80. The most important finding was that regression coefficients of the highest values were those that describe interactions between factors and that they differ for lipase and rhamnolipid production, which were both investigated in this study. Production of both metabolites was optimized and response equations were obtained, making it possible to predict rhamnolipid concentration or lipase activity from known values of the four factors. The highest achieved rhamnolipid concentration and lipase activity were 138 mg dm-3 (sunflower oil concentration 0.8 %, Tween? 80 concentration 0.05 %, temperature 30?C, and fermentation time 72 h) and 11111 IU dm-3(sunflower concentration of 0.4 %, Tween? 80 concentration of 0.05 %, temperature of 30?C, and fermentation time of 120 h), respectively.
Highlights
Pseudomonas aeruginosa has been repeatedly reported as a powerful producer of rhamnolipid biosurfactants as well as hydrolytic enzymes
Pseudomonas aeruginosa strains have been known as producers of rhamnolipids, microbial surfactants that deserve at least equal attention due to increasing areas for their utilization
The most important finding of this research related to rhamnolipid production was that regression coefficients of highest values were those that describe interactions between factors
Summary
Pseudomonas aeruginosa has been repeatedly reported as a powerful producer of rhamnolipid biosurfactants as well as hydrolytic enzymes. Pseudomonas aeruginosa is a gram-negative opportunistic pathogen, known for its ability to survive in a wide range of habitats such are water, plants, oil, etc. This ubiquitous environmental bacterium produces and secrets numerous virulence factors which conduce to its high environmental adaptability [1,2]. Other than highly applicable hydrolytic enzymes, Pseudomonas aeruginosa strains produce surface-active compounds known as rhamnolipids. This was firstly reported by Jarvis et al more than sixty years ago, but the chemical nature of these biosurfactants was not elucidated [10].
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