Effects of corn steep liquor on growth rate and pyrene degradation by Pseudomonas strains.

Department of Botany and Microbiology, University of Lagos, Akoka, Nigeria.
Current Microbiology (Impact Factor: 1.36). 12/2009; 60(6):407-11. DOI: 10.1007/s00284-009-9557-x
Source: PubMed

ABSTRACT The growth rates and pyrene degradation rates of Pseudomonas sp. LP1 and Pseudomonas aeruginosa LP5 were increased in corn steep liquor (CSL) supplemented. On pyrene alone the highest specific growth rate of LP1 was 0.018 h(-1), while on CSL-supplemented pyrene MSM, the value was 0.026 h(-)1. For LP5 the highest growth rate on CSL-supplemented pyrene-MSM was 0.034 h(-1). Conversely, on pyrene alone the highest rate was 0.024 h(-1). CSL led to marked reduction in residual pyrene. In the case of Pseudomonas sp. LP1 values of residual pyrene were 58.54 and 45.47%, respectively, for the unsupplemented and supplemented broth cultures, showing a difference of 13.09%. For LP5 the corresponding values were 64.01 and 26.96%, respectively, showing a difference of 37.05%. The rate of pyrene utilization by LP1 were 0.08 and 0.11 mg l(-1) h(-1) on unsupplemented and supplemented media, respectively. The corresponding values for LP5 were 0.07 and 0.015 mg l(-1) h(-1), respectively. These results suggest that CSL, a cheap and readily available waste product, could be very useful in the bioremediation of environments contaminated with pyrene.

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    ABSTRACT: Cryptococcus curvatus is able to grow on crude glycerol derived from the biodiesel production process. Through Box–Behnken design and response surface methodology, the optimal temperature, pH, and glycerol concentration for yeast growth and lipid production on pretreated crude glycerol was identified as 30.2 °C, 6.0, and 19.8 g/l, respectively. Adopting these optimal parameters, the biomass density obtained was 7.11 ± 0.36 g/l with a lipid content of 38.53 ± 1.88%, which matched well with predicted values of 6.98 g/l and 41.31%, respectively. The resulting parameters of the response surface method optimization were used in a fed-batch fermentation where crude glycerol was automatically pumped in responding to exhausted oxygen levels in the fermentor. At the end of 12 days, the biomass concentration was 44.53 g/l and the lipid content was 49.0%. Compared with our previous fed-batch experiment which was conducted under un-optimized condition and manual feeding, the yield of biomass and lipid increased 35.26% and 25.29%, respectively. The optimal parameters and the automatic pumping scheme developed from this study will assist greatly in future industrial scale application of producing microbial oils from crude glycerol.
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