Conclusions And Future Research

The use of anaerobes in industrial processes has grown dramatically over the past 20 years. Traditionally, anaerobes were used routinely in the processing of fermented foods such as lactic acid and propionic acid bacteria in cheeses, yogurts, sausages, and pickles. In waste treatment, mixed methanogenic cultures were used in both industrial and municipal anaerobic digestors for removal of residual organic matter.

Now, C. botulinum toxins are used as medicines. Numerous organic alcohols and acids are produced by industry as natural fermentation chemicals. These natural chemicals are used in flavors, fragrances, preservatives, and other specialty products. Fermentation-derived lactic acid is now produced by industry as a commodity chemical and is used as an acidulant, disinfectant, green solvent, and precursor for polylactide-based biodegradable plastics. Anaerobic composting systems are used to treat food and municipal solid wastes because they produce less end product that must be used or land spread. Sulfite is also removed from coal-bearing flue gases in bioreactor systems comprising mixed sulfidogenic cultures.

With the rapid growth in isolation and characterization of new anaerobic species from normal and extreme environments, the diversity of anaerobic species with unique biochemical attributes far surpasses that of aerobic microbes. This great diversity of anaerobic microbes should be expected since anaerobes were the first organisms to evolve on earth, yet they were the last large natural group to be studied in detail by biologists. The vast array of biochemical diversity shown by anaerobes is related in part to the fact that they are not limited to use of O2 as an electron acceptor, they can use fermentative metabolism or CO2, SO4, or other electron acceptors for anaerobic respiration. This biochemical diversity will undoubtably be exploited in the future since many of the fermentation products and enzymes of anaerobes are of interest to industry (i.e., food-feed, chemical, pharmaceutical, energy, and environmental companies).

Several research areas on anaerobes showing special industrial promise include succinate fermentation, ther-mozymes, and dechlorinating methanogenic granules. Ethanol fermentations are limited in part because two moles of CO2 are lost from the product per mole of glucose fermented. On the other hand, one can derive more than one pound of succinate per pound of glucose fermented because the theoretical chemical yield is 1 glucose + 2 CO2 + 2 H2 r 2 succinate. Succinate has a wide variety of uses as both a specialty chemical and commodity intermediate chemical. Perhaps the largest markets for succinate includes their use as a feedstock to produce stronger-than-steel engineered plastics and polyesters, and as the che-lator EDDS (ethylene diamine disuccinate) to replace nonbiodegradable EDTA.

The saccharolytic enzymes of thermoanaerobes are very active and stable. These thermozymes could be used to develop the next generation of enzymes used in the starch-processing industry (i.e., a-amylase, glucose isomerase, glucoamylase, and pullulanase) or to initiate a cellulose-processing industry for enhanced biomass utilization based on very active and stable cellulases and hemicellu-lases. Anaerobic sediments and soils are contaminated with a wide variety of chlorinated compounds. The use of dechlorinating methanogenic granules offers an alternative to expensive dredging and landfilling. Dechlorinating methanogenic granules can degrade a wide variety of toxicants (DDT, DIOXINS, PCE/TCE, PCBs, PCP, etc.) by in situ bioagumentation technology.

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