Barr D P, Aust S D
Biotechnology Center, Utah State University, Logan 84322-4705.
Rev Environ Contam Toxicol. 1994;138:49-72. doi: 10.1007/978-1-4612-2672-7_3.
The white rot fungi technology is very different from other more well-established methods of bioremediation (e.g., bacterial systems). The differences are primarily due to the mechanisms discussed previously. The unusual mechanisms used by the fungi provide them with several advantages for pollutant degradation, but the complexity of these mechanisms has also made the technology slow to emerge as a viable method of bioremediation. One distinct advantage that white rot fungi have over bacterial systems is that they do not require preconditioning to a particular pollutant. Bacteria must be preexposed to a pollutant to allow the enzymes that degrade the pollutant to be induced. The pollutant must also be present in a significant concentration, otherwise induction of enzyme synthesis will not occur. Therefore, there is a finite level to which pollutants can be degraded by bacteria. In contrast, the degradative enzymes of white rot fungi are induced by nutrient limitation. Thus, cultivate the fungus on a nutrient that is limited in something, and the degradative process will be initiated. Also, because the induction of the lignin-degrading system is not dependent on the chemical, pollutants are degraded to near-nondetectable levels by white rot fungi. Another unique feature of pollutant degradation by white rot fungi involves kinetics. The process of chemical conversion by these fungi occurs via a free-radical process, and thus the degradation of chemicals often follows pseudo-first-order kinetics. In fact, in several studies, it has been found that the rate of mineralization or disappearance of a pollutant is proportional to the concentration of the pollutant. This makes the time required to achieve decontamination more important than the rate of degradation. Because the metabolism of chemicals by bacteria involves mostly enzymatic conversions, pollutant degradation often follows Michaelis-Menton-type kinetics. Therefore, Km values of various degradative enzymes with respect to the pollutant must be considered when using bacteria for bioremediation. Considering this, the solubility of a pollutant or a mixture of pollutants might also present a problem for bacterial degradation. In contrast, using a nonspecific free-radical-based mechanism, the fungi are able to degrade insoluble complex mixtures of pollutants, such as creosote (Aust and Bumpus 1989) and Arochlor (Bumpus and Aust 1987b). Inexpensive nutrient sources, such as sawdust, wood chips, surplus grains, and agricultural wastes, can be used to effectively cultivate white rot fungi.(ABSTRACT TRUNCATED AT 400 WORDS)
白腐真菌技术与其他更成熟的生物修复方法（如细菌系统）有很大不同。这些差异主要归因于前文讨论的机制。真菌所采用的独特机制使其在污染物降解方面具有若干优势，但这些机制的复杂性也导致该技术作为一种可行的生物修复方法发展缓慢。白腐真菌相对于细菌系统的一个明显优势是它们不需要对特定污染物进行预处理。细菌必须预先接触污染物，以使降解污染物的酶得以诱导产生。污染物还必须以显著浓度存在，否则酶合成的诱导就不会发生。因此，细菌对污染物的降解存在一个有限的水平。相比之下，白腐真菌的降解酶是由营养限制诱导产生的。因此，在某种营养有限的物质上培养真菌，降解过程就会启动。此外，由于木质素降解系统的诱导不依赖于化学物质，白腐真菌能将污染物降解到几乎检测不到的水平。白腐真菌降解污染物的另一个独特特征涉及动力学。这些真菌的化学转化过程通过自由基过程发生，因此化学物质的降解通常遵循准一级动力学。事实上，在多项研究中发现，污染物的矿化或消失速率与污染物浓度成正比。这使得实现去污所需的时间比降解速率更重要。因为细菌对化学物质的代谢主要涉及酶促转化，污染物降解通常遵循米氏动力学。因此，在使用细菌进行生物修复时，必须考虑各种降解酶相对于污染物的米氏常数。考虑到这一点，污染物或污染物混合物的溶解度对于细菌降解也可能是个问题。相比之下，利用基于非特异性自由基的机制，真菌能够降解不溶性的复杂污染物混合物，如杂酚油（奥斯特和邦普斯，1989年）和多氯联苯（邦普斯和奥斯特，1987b）。廉价的营养源，如锯末、木片、剩余谷物和农业废弃物，可用于有效培养白腐真菌。（摘要截选至400字）
