David Kafkewitz

Aerobic degradation and dechlorination of 2–chlorophenol, 3‐chlorophenol and 4‐chlorophenol by a Pseudomonas pickettii strain

F. FAVA, P.M. ARMENANTE AND D. KAFKEWITZ. 1995. A Gram‐negative aerobic bacterium capable of using 2–chlorophenol (2–CP), 3–chlorophenol (3–CP) and 4–chlorophenol (4–CP) as sole carbon sources was isolated and characterized. The bacterium, designated LD1, was identified to be a Pseudomonas pickettii strain. LD1 was able to totally degrade and dechlorinate 2–CP (initial concentration: 1.51 mmol I‐1), 3–CP (initial concentration: 0.57 mmol I‐1) and 4–CP (initial concentration: 0.75 mmol I‐1) within 30, 30 and 40 h of incubation, respectively, under growing‐cell batch conditions. LD1 was also found to be able to metabolize chlorocatechols in growing‐ and resting‐cell conditions. This suggests that the bacterium degrades monochlorophenols through a chlorocatechol pathway. In addition, LD1 was found to be capable of readily metabolizing other organic compounds such as phenol, benzoic acid, hydroxybenzoic acids and hydroquinone.

Influence of organic and inorganic growth supplements on the aerobic biodegradation of chlorobenzoic acids

The effect of yeast extract and its less complex substituents on the rate of aerobic dechlorination of 2-chlorobenzoic acid (2-ClBzOH) and 2,5-dichlorobenzoic acid (2,5-Cl2BzOH) by Pseudomonas sp. CPE2 strain, and of 3-chlorobenzoic acid (3-ClBzOH), 4-chlorobenzoic acid (4-ClBzOH) and 3,4-dichlorobenzoic acid (3,4-Cl2BzOH) by Alcaligenes sp. CPE3 strain were investigated. Yeast extract at 50 mg/l increased the average dechlorination rate of 200 mg/l of 4-ClBzOH, 2,5-Cl2BzOH, 3,4-Cl2BzOH, 3-ClBzOH and 2-ClBzOH by about 75%, 70%, 55%, 7%, and 1%, respectively. However, in the presence of yeast extract the specific dechlorination activity of CPE2 and CPE3 cells (per unit biomass) was always lower than without yeast extract, although it increased significantly during the exponential growth phase. When a mixed vitamin solution or a mixed trace element solution was used instead of yeast extract the rate of 4-ClBzOH dechlorination increased by 30%–35%, whereas the rate of 2,5-Cl2BzOH and 3,4-Cl2BzOH dechlorination increased by only 2%–10%. The presence of vitamins or trace elements also resulted in a specific dechlorination activity that was generally higher than that observed for the same cells grown solely on chlorobenzoic acid. The results of this work indicate that yeast extract, a complex mixture of readily oxidizable carbon sources, vitamins, and trace elements, enhances the growth and the dechlorination activity of CPE2 and CPE3 cells, thus resulting in an overall increase in the rate of chlorobenzoic acid utilization and dechlorination.

Effect of pH on the anaerobic dechlorination of chlorophenols in a defined medium

Anaerobic dehalogenation of aromatic compounds is a well-documented phenomenon. However, the effects of operating parameters such as pH have received little attention despite their potential impact on treatment processes using dehalogenating organisms. In this work the effect of pH on the dehalogenation of 2,4,6-trichlorophenol (2,4,6-TCP) was studied using defined media containing one of several non-fermentable buffering agents (MOPS, TRICINE, BICINE, CHES), and no chloride ions. The dechlorination process was followed by monitoring the disappearance of 2,4,6-TCP, as well as the appearance of its dehalogenation products, i.e., 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP), and chloride ions. The results indicate that dechlorination occurs only if the pH is within the range 8.0–8.8. The newly formed 2,4-DCP was also dehalogenated in the process. However, even within this pH range dechlorination ceased when all 2,4,6-TCP and 2,4-DCP was converted to 4-CP. Stoichiometric amounts of all dehalogenation products (including chloride) could be recovered at any stage during the process. In addition, the biomass concentration was measured. After an initial lag phase, it appeared that the rate of dechlorination per unit biomass (proportional to the Cl− concentration divided by the biomass concentration) went through a rapid increase and then remained constant throughout the process. This indicates that the dechlorinating organism(s) either make up the entire population or constitute a stable fraction of it.

Rapid dehalogenation of 2,4,6-trichlorophenol at alkaline pH by an anaerobic enrichment culture

An enrichment culture, derived from the anaerobic stage of a two‐step sequential anaerobic‐aerobic reactor system which mineralized 2,4,6‐trichlorophenol, stoichiometrically converted 2,4,6‐trichlorophenol to 4‐chlorophenol. Dehalogenation occurred only in alkaline media (pH 8–9) at concentrations of substrate up to 1 mmol 11. Formate plus acetate or trypticase could serve as electron donors. Neither vitamins nor trace elements were required in a chloride‐free defined medium. The dehalogenating organism was oxygen‐resistant, but was not active in media which were oxidized with respect to resazurin indicator dye. Most probable number counts of the dehalogenating cultures showed that the dehalogenating organisms were present in very small numbers, yet catalysed dehalogenation at rates considerably faster than other dehalogenating organisms described in the literature.

Effect of vitamins on the aerobic degradation of 2-chlorophenol, 4-chlorophenol, and 4-chlorobiphenyl.

The effect of vitamins on the aerobic degradation and dechlorination of 2-chlorophenol and 4-chlorophenol by Pseudomonas picketti, strain LD1, and 4-chlorobiphenyl by Pseudomonas sp. strain CPE1 was determined. These microorganisms are capable of using the target compounds as the sole carbon and energy source, but do not need vitamins to metabolize them. The addition to the culture medium of a vitamin solution containing biotin, folic acid, pyridoxine hydrochloride, riboflavin, thiamine hydrochloride, niacin, pantothenic acid, cyanocobalamin, p-aminobenzoic acid, and thioctic acid (total final concentration: ≤ 600 ppb) resulted in a 7%–16% increase in the amount of target compounds degraded over the incubation period required for the concentration of the compound in the cultures to drop to approximately zero. A corresponding increase in the amount of chloride ion produced was also detected during the same period, indicating active (and often stoichiometric) dechlorination of the target compounds.

Dehalogenation and mineralization of 2,4,6-trichlorophenol by the sequential activity of anaerobic and aerobic microbial populations

SummaryA sequential anaerobic-aerobic treatment process that can mineralize 2,4,6-trichlorophenol has been developed. The process uses diluted anaerobic digester fluid as a culture medium, and a single microbial population enriched from the digester fluid for both the anaerobic and aerobic steps.

Antilymphoma Activity of a Glutaminase-Free L-Asparaginase of Microbial Origin

Summary The antilymphoma activity and blood clearance behavior of the glutamin-ase-free L-asparaginase from Vibrio succino-genes was tested in C3H mice with transplanted 6C3HED lymphosarcoma. Seven animals in which tumors had been implanted 12 days earlier each received two ip injections of 0.33 IU of homogeneous enzyme per day over a 4-day period. All animals appeared to be in complete regression 3 days after the injections were terminated and showed regression profiles that were at least comparable to those obtained with a second group of 6C3HED mice injected with equivalent levels of EC-2 L-asparaginase. The tumors did not return within 30 days in the enzyme-treated groups, whereas all animals injected with buffer or heat-inactivated V. succinogenes enzyme died during this period. Half-lives of 17-42 hr were observed for the V. succinogenes L-asparaginase in the blood stream of eight tumor-bearing mice. These results demonstrate that the L-asparaginase from V. succinogenes is an effective antilymphoma agent. We thank David Lester and David E. Mallon for assistance with the statistical analyses and K. Sieglinde Neuhauser for aid with the tumor measurements.

Toluene and xylene degradation by a denitrifying strain of Xanthomonas maltophilia with limited or no oxygen

A strain of Xanthomonas (Pseudomonas) maltophilia utilized toluene and xylene at the same rate in a well-mixed system containing excess nitrate and either 2% oxygen or no oxygen. Toluene utilization was much more rapid when 20% oxygen was provided. The data presented, as well as data in the literature, suggest that for the degradation of these aromatic hydrocarbons, limited amounts of oxygen provide no advantage over anoxic denitrification.

Effect of a biofilm on the adsorption of 4-chlorophenol on activated carbon

Abstract  The adsorption of 4-chlorophenol (4-CP) on activated carbon was studied experimentally both in the presence and in the absence of an inactivated anaerobic biofilm on the surface of carbon pellets. The presence of the biofilm markedly decreased the rate of 4-CP adsorption. However, the final near-equilibrium state (at 27 h) was not affected, and the incremental amount of material adsorbed on the pellets was similar both in the presence and in the absence of the biofilm. The biosorption of 4-CP by a biofilm coating non-adsorbing pellets was also determined. It appears that the biofilm also has some adsorption capability. Freundlich-type equations were used to correlate all data, and transient and near-equilibrium isotherms were obtained for 4-CP adsorption on different adsorbing materials at different times.

Polyphenol oxidase activity in the roots of seedlings of Bromus (Poaceae) and other grass genera

UNLABELLED PREMISE OF THE STUDY Phenolic compounds exuded by roots have been implicated in allelopathic interactions among plants. Root enzymes that destroy phenolics may protect plants against allelopathic inhibition and thus may aid in invasiveness. Phenolic-degrading enzymes are chiefly found in aboveground plant parts, but have also been previously reported in root tissues where the enzymes function is unknown. We explored phenolic oxidase activity in emerging roots of grasses in a survey across different grass genera; in particular, we aimed to test whether grasses of the genus Bromus, known for their large invasion potential, differ in this respect from other grass taxa. • METHODS We assayed a range of grass genera commonly found in the United States for root enzyme activity with spectrophotometric assays of phenol oxidase activity using l-DOPA as the main substrate. • KEY RESULTS In the survey of a grass genera, we discovered that roots of the genus Bromus contain large amounts of polyphenol oxidase (PPO) activity, while all other tested grass genera, even ones closely related to Bromus, did not. PPO was found to be present at germination and remained active throughout the life of the plant. Compared to other PPOs, the enzyme present in Bromus appears to have a narrow substrate range. • CONCLUSIONS The specific functions of the root PPO and the ecological ramifications of the special status of Bromus are not yet clear. The possibility that the enzyme plays a role in plant species interaction for bromes, a genus of grasses known to have high invasive potential, is raised.