Enhancement of Carbofuran Degradation by Soil Enrichment Cultures, Bacterial Cultures and by Synergistic Interaction among Bacterial Cultures

Enhancement of Carbofuran Degradation by Soil Enrichment Cultures, Bacterial Cultures and by Synergistic Interaction among Bacterial Cultures

Enhancement of Carbofuran Degradation by Soil Enrichment Cultures, Bacterial Cultures and by Synergistic Interaction among Bacterial Cultures

Abstract: Pseudomonas putida KT2442 is able to accumulate medium-chain-length poly(3-hydroxyalkanoates)
(mcl-PHAs) as intracellular inclusions on a variety of fatty
acids and many other carbon sources. Some of these
substrates, such as octanoic acid, alkenoic acids, and halogenated derivatives, are toxic when present in excess.
Efficient production of mcl-PHAs on such toxic substrates therefore requires control of the carbon source
concentration in the supernatant. In this study, we develop a closed-loop control system based on on-line gas
chromatography to maintain continuously fed substrates
at desired levels. We used the graphical programming
environment LABVIEW to set up a flexible process control system that allows users to perform supervisory process control and permits remote access to the fermentation system over the internet. Single-substrate supernatant concentration in a high-cell-density fed-batch
fermentation process was controlled by a proportional
(P) controller (P = 50%) acting on the substrate pump
feed rate. Na-octanoate concentrations oscillated around
the setpoint of 10 mM and could be maintained between
0 and 25 mM at substrate uptake rates as high as 90
mmol L−1 h
−1. Under cofeeding conditions Na-10-
undecenoate and Na-octanoate could be individually
controlled at 2.5 mMand 9 mM,respectively, by applying
a proportional integral (PI) controller for each substrate.
The resulting copolymer contained 43.5 mol% unsaturated monomers and reflected the ratio of 10-undecenoate
in the feed. It was suggested that both substrates were
consumed at similar rates. These results show that this
control system is suitable for avoiding substrate toxicity
and supplying carbon substrates for growth and mclPHA accumulation.

read online

Post Comment