Phenol-degrading abilities of bacteria and fungi have been deeply studied compared to those in algae. Out of the six microalgae isolates, C.pyrenoidosa and diatom BD1IITG showed significant ability for phenol degradation, showing prospective application for phenol remediation. The growth and phenol degradation dynamics of two powerful algal strains C.pyrenoidosa and diatom BD1IITG were analyzed by growth kinetic modeling.
Pre-adaptation of C.pyrenoidosa to the target phenol concentration is used as a strategy to further increase growth (0.078 h-1) and phenol degradation rate (0.636 h-1). This present work reports for the first time the complete pathway of phenol degradation in Chlorella pyrenoidosa and the diatom BD1IITG using HPLC, LC-MS and UV-visible spectrophotometry. Phenol hydroxylase is the first enzyme that causes the initial attack on phenol in the phenol degradation pathway.
Phenol degradation by microalgae has been less studied compared to other microbial strains and therefore deserves further attention. The lack of information on the metabolic mechanism of phenol degradation in green unicellular algae requires adequate research in this direction.
Introduction 3-8
Photodecomposition 15
Biokinetic parameters of maximal specific cell growth rate μmax, substrate affinity constant Ks, and substrate inhibition constant KI vary over a wide range depending on cell type and culture media (Banerjee and Ghoshal 2010). The KS value (half-saturation coefficient) indicates the affinity of the microorganism to the substrate. The biosensor showed linearity between the maximum oxygen consumption rate and phenol concentration in the phenol concentration range of 2.5-400 μM at 40 0C and pH 7.6. The response time of the biosensor was 10 sec, which is relatively short. The commercial applicability of the mixtophytic culture process is hindered by the high cost of the substrate which accounts for 50% of the cost of the culture medium (Yang et al. 2011). The solution to this obstacle of high costs caused by mycotrophic algal cultivation is to use alternative inexpensive substrates.
To evaluate the kinetics of phenolic degradation, phenolic degradation is performed at optimal phenolic concentration (i.e., the concentration with the highest growth and phenolic degradation rate) using optimal biomass concentration, pH and photoperiodicity as obtained from the previous experiments described in Section 2.2.2. The high bootstrap support from the phylogenetic tree (Figure 3.2 b) showed that the isolate BD1IITG belongs to the algal group diatoms due to a close evolutionary relationship with diatoms EJ10-B11-11A. The 16S rRNA gene sequence of diatom BD1IITG was deposited to NCBI GenBank and an accession no. Attempts were also made to understand the dynamics of biomass growth and phenol degradation by C.pyrenoidosa in refinery wastewater.
Refinery wastewater may contain other constituents that may prove inhibitory to the phenol-degrading potential of microorganisms (Agarry et al. 2008). Biomass growth and phenol degradation profile of C.pyrenoidosa cells acclimated to phenol are shown in Figure 3.10 (a)-(z). With this aim of achieving higher degradation rates, C.pyrenoidosa cells previously adapted to 250 mg/l (i.e., the concentration with the highest growth and phenol degradation rate) were used to degrade 250 mg/l phenol under the optimized.
To test the practical applicability of the process, previously adapted C.pyrenoidosa cells were used to degrade phenol in oil refinery wastewater.
Advanced oxidation processes 15
Adsorption 16
Liquid phase adsorption of phenol from water has been performed with silica gel, activated carbon, activated alumina (Roostaei and Tezel 2004), sawdust, polymerized sawdust, sawdust carbon (Jadhav and Vanjara 2004); hyacinth (Uddin et al. 2007);.
Electro-Fenton method 16
For the development of the phenol bioremediation process it is necessary to know the kinetics of growth and degradation of phenol. Involvement of the ortho pathway for phenol degradation has been reported in eukaryotes such as Trichosporon cutaneum. The involvement of the ortho pathway for phenol degradation has been reported in Trichosporon cutaneum (Neujhar and Gaal 1973).
The involvement of the ortho pathway in phenol degradation has been reported in (Neujhar and Gaal 1973), Penicillium sp. Because phenol hydroxylase is the first enzyme to cause an initial attack on phenol in the phenol degradation pathway, knowledge of its kinetic properties is of paramount importance for its potential applications (Pessione et al. 1999). Microbial degradation of phenol is a strong function of biomass growth and thus knowledge of growth kinetics is valuable information leading to insight into the microbe's capacity for phenol degradation (Kumar et al. 2005).
A strain with a high growth and phenol degradation rate is an important requirement for its practical applicability in the treatment of phenol in wastewater. The phenol degradation ability of acclimated microalgae cells was analyzed in the phenol concentration range of 50–1250 mg/L. Photodependency of phenol degradation has been reported in algal species such as Scenedesmus obliquus (Feng et al. 2013) and Chlorella vulgaris (Scragg 2006).
To analyze the effect of pH, biomass growth and phenol degradation were investigated in the pH range 4–9 of the culture medium.
Purification of phenol hydroxylase 57
Electrophoresis: enzyme homogeneity, molecular weight
Peptide mass fingerprinting of the purified protein 58
Absorption characteristics of flavoproteins 58
Effect of NADH as cofactor on phenol hydroxylation activity 58
Stoichiometry of reaction with phenol 59
Substrate affinity of purified enzyme towards phenol 59
Effect of pH and temperature on enzyme activity 59
Effect of chealators, heavy metals, denaturant and oxidizing agent
Multisubstrate specificity of purified enzyme 60
Storage stability of phenol hydroxylase 61
Results and Discussion 62-175
Screening and characterization of phenol degradation by potent algal
Efforts were also made to analyze the dynamics of biomass growth and phenolic degradation of the diatom BD1IITG in refinery wastewater. Based on the complete phenol degradation ability of C.pyrenoidosa, this strain was selected for further studies. As seen from Figure 3.19 c, neutral lipid content increased at a faster rate in pre-adapted C.pyrenoidosa cells used for phenol degradation compared to control cells.
Since the cells were pre-adapted to 250 mg/L phenol, we also attempted to analyze the dynamics of growth and phenol degradation of C.pyrenoidosa in 250 mg/L phenol-containing refinery water. The lipid productivity of C.pyrenoidosa during the degradation process of phenol in wastewater was found to be higher than that of 3026.7 mg/l/day obtained in nutrient media (Figure 3.22 c).
