Certain cellulolytic microbes (i.e., Clostridium, Acetivibrio, Bacteroides, and Ruminococcus) produce an intricate self-assembly of multi-enzyme complexes, called cellulosomes, which hydrolyze cellulosic and hemicellulosic biomass. Cellulosomes essentially consist of a non-enzymatic scaffolding protein associated with several enzyme subunits that act in concert to degrade biomass. There has been recent interest in constructing designer mini-cellulosomes, or nanosomes, to enhance synergistic interaction between enzyme components.

Cellobiohydrolase (CBH) and β-glucosidase (BG) are two important classes of glucosyl hydrolases that have significant synergistic interaction between each other. However, the interaction between the two enzymes is diffusion limited. One way of further improving the proximity synergistic action of CBH and BG is to construct nanosomes with the two enzymes co-immobilized. Nanoparticles such as carbon nanotubes (CNT) and polymeric nanoparticles, provide a suitable scaffold whose surface properties can be modified to immobilize enzymes. We have developed a nanosome with co-immobilized β-glucosidase and cellobiohydrolase. The enzymatic activity of the nanosome is measured using soluble (i.e., oligosaccharides) and insoluble substrates (i.e., crystalline cellulose). The nanosome is further studied using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Enzyme deposition on nanoparticles was further characterized by fluorescence confocal microscopy and change in the zeta (ζ) potential of nanoparticles due to enzyme adsorption on the surface. Enzyme loading was determined using UV-absorption spectroscopy.

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