How Microbes Are Able to Modify Aromatic Compounds

Furfuryl alcohol is the major ingredient in FURAN foundry binders. The flexibility of furfuryl alcohol as a binder base is enormous. Today furfuryl alcohol is used in binders for HOT-BOX, WARM BOX and gas hardened processes as well as in the traditional FURAN-NO-BAKE system.

• Furan NO-BAKE (FNB) was introduced in 1958.

It is suitable for making all types of metal castings in all sizes, and particularly used for the production of molds and larger cores. This acid catalyzed cold setting binder consist of a hardening catalysts such as sulfuric acids, sulfonic acids and phosphoric acids and of a reactive furan-type resin.

FNB is known for its superior shakeout characteristics and the sand can be reused by thermal and/or mechanical reclamation.

• Furan HOT BOX process uses furan resins in combination with a latent acid catalysts, e.g. ammonium salts.

The WARM BOX process is operated at lower temperatures and was developed by the Quaker Oats Company for the rapid production of cores in existing hot box equipment.

This type of furan binder contains more furfuryl alcohol than in hot box furan binders. A latent copper salt catalyst is used to cure the binder very rapidly upon heating.

• The Furan SO2 process is a gas cured binder system for the rapid production of small moulds and cores.

Curing of the furanic resin occurs right away, when the sand mix is exposed to SO2 gas at room temperature.

FA is used in other purpose like, Corrosion resistant fiber-reinforced plastics, Corrosion resistant cements and mortars, Reactive solvent for phenolic resins in the refractory industry, Chemical building block for drug synthesis, Paint stripper and cleaning compound formulation, Viscosity reducer for epoxy resins, Chemical feedstock for 5-membered oxygen heterocycles, and Wood Modification.

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Degrading aromatic compounds has now become a challenge due to its structural complexity and stability. Different chemical technologies have been employed for the reduction of aromatic compounds contained effluents but this technique have proven to be costly and produce secondary toxic pollutants. Thus, biological treatments become a favourable alternative due to its cost effectiveness, potentiality and turn hazardous materials into harmless products [Ali, Namane and Hellal 2013]. In view of the various uses of FA, it is apparent that there will be spill or discharge of FA or PFA in the environment. This in turn will have hazardous effect on living being and the whole environment, so it is necessary to degrade FA.

Biodegradation is an effective remediation technology for these aromatic organic pollutants. Metabolic versatility of microorganisms is a blessing for biodegradation of hazardous pollutants. A viable remedial technology requires quick adaptation capable microorganisms and efficient uses of pollutants of interest in a particular case in a reasonable period of time [Seo et al. 2009]. Many factors are influence microorganisms to use pollutants as substrates or cometabolize them. Biodegradation is a very broad field and involves uses of a wide range of microorganisms to break chemical bonds.

The breakdown of aromatic compounds by ring cleavage is an essential biochemical step in Nature’s ‘carbon’ cycle and is performed by several kinds of microorganism. Bacteria are the most versatile in this respect, but several yeasts and fungi are able to degrade a more limited range of benzenoid structures.

Among the eubacteria, representatives of the families Coccaceae, Mycobacteriaceae, Pseudomonadaceae, Spirillaceae, Bacteriaceae and Bacillaceae are active in this respect. The yeasts Oospora, Candida, Debaromyces, Pichia and Saccharomyces grow in media with catechol as sole carbon source. Certain higher fungi, e.g. Aspergillus, Penicillium and Neurospora attack aromatics and a variety of soil and wood-rotting fungi dissimilate the aromatic polymer lignin, as well as other plant phenolics. In all the above cases of aromatic ring metabolism, molecular oxygen is an obligatory oxidant.

The photosynthetic bacteria Rhodopseudomonas and some Rhodospirillum strains utilize benzoate under strictly anaerobic conditions in the light. Finally, there exists an anaerobic type of aromatic ring metabo1ism-e.g. the so-called methane fermentation of benzoate, although it is doubtful whether these methane bacteria are in pure culture.

These microbes produce, mostly as a result of induction, a whole sequence of enzymes which convert aromatic substrates into an ortho or para dihydroxyphenol derivative, followed by cleavage of the ring to aliphatic acids; these ring fission products are then funnelled into the Krebs cycle through a variety of pathways, depending on the organism and cultural conditions.

The distinctive biochemical step is ring cleavage. There are many instances of microbes being able to modify aromatic compounds, either by hydroxylation, or elimination of substituent groups, without necessarily causing fission. In the case of the aromatic amino acids, phenylalanine, tyrosine and tryptophan, pathways of metabolism exist that have much in common in all forms of life. It is only possible to sketch the salient features of microbial aromatic ring metabolism here, since the topic has, of recent years, greatly increased in scope.

There are many aerobic bacteria that are capable to degrade aromatic compounds. These aerobic bacteria are used aromatic compounds as their sole carbon and energy source [Yang and Humphery 1975]. There are various researches and reviews claim that Pseudomonas is an effective bacteria which have capacity to degrade many aromatic compounds. Pseudomonas is a genus of Gram-negative, rod-shaped bacteria. They are aerobic and non-sporulating with one or more polar flagella for motility. There are currently 218 species assigned to Pseudomonas and the genus has considerable heterogeneity.

Pseudomonas contains a number of scientifically and medically studied bacteria, such as the opportunistic pathogen P. aeruginosa, and there is increasing availability of Pseudomonas strain genome sequences. Pseudomonas is well known for its metabolic versatility, being able to utilize an unusually wide range of organic compounds.

Certain members of the genus are

• able to metabolize pollutants,
• including P. fluorescens,
• P. putida,
• P. aeruginosa,
• P. cepacia,
• P. vesicularis, and
• P. paucimobilis.

As a result, they are often isolated and studied for their bioremediation capabilities. In the literature of Montrio et al. have reported that Pseudomonas putida as a representative of aromatic degrader of aromatics, especially phenol. In the literature of Juang and Tsai, Chandana Lakshmi et al. are documented that P. putida is a very well degrader of Phenol. There are various report are present which claim that P. aeruginosa is also a well degrader of various aromatic hydrocarbons

Biodegradation of FA and PFA has not been explore earlier. There is not a single report present yet showing the Furfuryl alcohol degradation by microbes. But there is a lot of literature in which degradation phenol has been done by microbes. FA has similar aromatic chemical structure as that of phenol so the same concept can be applied for the FA. Aromatic compounds degradation is sensitive to many factors such as pH, incubation periods, carbon and nitrogen sources, and enormous efforts in several studies have been made to obtain the optimal conditions that increase the efficiency of Aromatic compounds degrading bacteria.

Therefore, the present study aims at optimizing the parameters affecting FA degradation by Pseudomonas putida (MTCC 1194) and Pseudomonas aeruginosa (MTCC 1034). In this study, degradation studies were carried out with different concentrations of FA in the suitable growth medium.