Potential of biofilm-based biofuel production

Biodegradation of aromatic compounds: current status and opportunities for biomolecular approaches

Biodegradation can achieve complete and cost-effective elimination of aromatic pollutants through harnessing diverse microbial metabolic processes. Aromatics biodegradation plays an important role in environmental cleanup and has been extensively studied since the inception of biodegradation. These studies, however, are diverse and scattered; there is an imperative need to consolidate, summarize, and review the current status of aromatics biodegradation. The first part of this review briefly discusses the catabolic mechanisms and describes the current status of aromatics biodegradation. Emphasis is placed on monocyclic, polycyclic, and chlorinated aromatic hydrocarbons because they are the most prevalent aromatic contaminants in the environment. Among monocyclic aromatic hydrocarbons, benzene, toluene, ethylbenzene, and xylene; phenylacetic acid; and structurally related aromatic compounds are highlighted. In addition, biofilms and their applications in biodegradation of aromatic compounds are briefly discussed. In recent years, various biomolecular approaches have been applied to design and understand microorganisms for enhanced biodegradation. In the second part of this review, biomolecular approaches, their applications in aromatics biodegradation, and associated biosafety issues are discussed. Particular attention is given to the applications of metabolic engineering, protein engineering, and "omics" technologies in aromatics biodegradation.

Cell immobilization for production of lactic acid biofilms do it naturally

Interest in natural cell immobilization or biofilms for lactic acid fermentation has developed considerably over the last few decades. Many studies report the benefits associated with biofilms as industrial methods for food production and for wastewater treatment, since the formation represents a protective means of microbial growth offering survival advantages to cells in toxic environments. The formation of biofilms is a natural process in which microbial cells adsorb to a support without chemicals or polymers that entrap the cells and is dependent on the reactor environment, microorganism, and characteristics of the support. These unique characteristics enable biofilms to cause chronic infections, disease, food spoilage, and devastating effects as in microbial corrosion. Their distinct resistance to toxicity, high biomass potential, and improved stability over cells in suspension make biofilms a good tool for improving the industrial economics of biological lactic acid production. Lactic acid bacteria and specific filamentous fungi are the main sources of biological lactic acid. Over the past two decades, studies have focused on improving the lactic acid volumetric productivity through reactor design development, new support materials, and improvements in microbial production strains. To illustrate the operational designs applied to the natural immobilization of lactic acid producing microorganisms, this chapter presents the results of a search for optimum parameters and how they are affected by the physical, chemical, and biological variables of the process. We will place particular emphasis upon the relationship between lactic acid productivity attained by various types of reactors, supports, media formulations, and lactic acid producing microorganisms.

Microbial biofilms: a concept for industrial catalysis?

Biofilm reactors have long been commercially used in the treatment of wastewater and off-gas. New opportunities are arising with the rapid expansion of our understanding of biofilm biology over the last few years. Biofilms have great potential as industrial workhorses for the sustainable production of chemicals because of their inherent characteristics of self-immobilization, high resistance to reactants and long-term activity, which all facilitate continuous processing. A variety of biofilm reactor configurations have been explored for productive catalysis and some reactors have been operated continuously for months. Sectors that might particularly benefit from this biofilm approach include synthetic chemistry (ranging from specialty to bulk chemicals), bioenergy, biologics and the food industry.