VANILLIN PRODUCTION toxicity

The biocatalytic reduction of carboxylic acids to their respective aldehydes or alcohols is a relatively new biocatalytic process with the potential to replace conventional chemical processes that use toxic metal catalysts and noxious reagents. An enzyme known as carboxylic acid reductase (Car) from Nocardia sp. NRRL 5646 was cloned into Escherichia coli BL21(DE3). This E. coli based biocatalyst grows faster, expresses Car, and produces fewer side products than Nocardia. Although the enzyme itself can be used in small-scale reactions, whole E. coli cells containing Car and the natural cofactors ATP and NADPH, are easily used to reduce a wide range of carboxylic acids, conceivably at any scale. The biocatalytic reduction of vanillic acid to the commercially valuable product vanillin is used to illustrate the ease and efficiency of the recombinant Car E. coli reduction system." A comprehensive overview is given in Reference 6, and experimental details below are taken primarily from Reference 7. 

Wastewaters contaming aromatic organic compounds must be pre-treated be re they are discharged into conventional waste treatment systems. A variety of these compounds are reftactory, toxic and. inhibitory in nature. The purpose of the pretreatment is to remove or reduce these compounds to less toxic or more biodegradable mtermediate products which can be treated by conventional biological methods (6). Examples of organic compounds that are toxic in nature are resorcmol, vanillin and salicylic acid. 

Extracts of certain soils, especially of muck and bog soils, and sometimes of forest soils (Persidsky and Wilde, 1954) have frequently been shown to be toxic. Toxicity in such cases may be either of chemical or microbial origin depending both upon the soil itself and on the conditions under which it existed in nature. In fact, some of the first work on toxicity was done by Schreiner and Shorey in 1909 when they attempted to explain the low productivity of certain soils. They isolated dehydroxystearic acid and vanillin and showed them to be toxic to plants in aqueous solution. Undoubtedly they overemphasized the practical importance of these compounds, but they at least demonstrated at an early date that toxic organic materials do exist in soils. 

Examples illustrate the rapidly-growing and promising uses of cydodextrins in various operations the intensification of the conversion of hydrocortisone to prednisolone, the improvement in the yield of fermentation of lankaci-dine and podophyllotoxin, the stereoselective reduction of benzaldehyde to L-phenylacetyl carbinol, and the reduction in toxicity of vanillin to yeast, or organic toxic substances to detoxificating microorganisms. In the presence of an appropriate cyclodextrin derivative (e.g., 2,6-dimethyl-(3-cyclodextrin), lipid-like inhibitor substances are complexed. The propagation of Bordatella pertussis and the production of pertussis toxin therefore increases up to hundred-fold. Cydodextrins and their fatty acid complexes can substitute for mammalian serum in tissue cultures. 

Vanillin is a flavoring agent used in syrups, ice cream, and other edible products. Xuebao Fine Chemicals Co. Ltd. (China) used to manufacture vanillin from o-nitro chlorobenzene. The process produced toxic chemicals, three to five different tars, high CODs, high VOCs, high health and safety risks, and unacceptable standards for a flavoring product. The plant dumped untreated effluents into a nearby river, and toxic tars were stockpiled in unmonitored landfills. Rhodia Chemicals purchased Xuebao in 2000. The process was modified so that it is now based on the catechol route (see Fig. 9.29). This process does not produce any waste and uses several heterogeneous catalysts. 

Due to its properties and low toxicity, FA is now widely used in the food and cosmetic industries. It serves as the raw material for the production of vanillin and preservatives, as a cross-linking agent for the preparation of food gels and edible Aims, and as an ingredient in sports foods and skin protection agents. 

The vanillin in the mixture is not a natural product. Natural vanilla extract is a mixture of hundreds of compounds in addition to vanillin. Artificial vanilla flavoring is a solution of pure synthesized vanillin, 4-hydroxy-3-methoxybenzaldehyde. Mixtures of vanillin with other toxicants enhance mutagenic effects [29] and produce synergistic inhibition of hgnoceUulose degradation when mixed with catechol [30]. 

The preservative BHT has been shown to have adverse effects on the liver and limgs [68, 69]. When mixed with another preservative, BHA, the BHA/BHT mixture enhances the limg toxicity. In another study, it was shown that BHA, eugenol methyl paraben, vanillin, gnaiacol, ferulic add, and other phenolic compounds used in food products enhanced the in vitro peroxidase-catalyzed covalent bonding of BHT to microsomal protein and the formation of BHT-qninone methide [70]. 

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