Engineering of a chitosanase fused to a carbohydrate-binding module for continuous production of desirable chitooligosaccharides

Chitooligosaccharides (CHOS) with multiple biological activities are usually produced through enzymatic hydrolysis of chitosan or chitin. However, purification and recycling of the enzyme have largely limited the advancement of CHOS bioproduction. Here, we engineered a novel enzyme by fusing the native chitosanase Csn75 with a carbohydrate-binding module (CBM) that can specifically bind to curdlan. The recombinase Csn75-CBM was successfully expressed by Pichia pastoris and allowed one-step purification and immobilization in the chitosanase immobilized curdlan packed-bed reactor (CICPR), where a maximum adsorption capacity of 39.59 mg enzyme/g curdlan was achieved. CHOS with degrees of polymerization of 2-5 (a hydrolysis yield of 97.75%), 3-6 (75.45%), and 3-7 (73.2%) were continuously produced by adjusting the ratio of enzyme and chitosan or the flow rate of chitosan. Moreover, the CICPR exhibited good stability and reusability after several cycles. The recombinase Csn75-CBM has greatly improved the efficiency of the bioproduction of CHOS.

Synthesis of a precursor of D-fagomine by immobilized fructose-6-phosphate aldolase

Fructose-6-phosphate aldolase (FSA) is an important enzyme for the C-C bond-forming reactions in organic synthesis. The present work is focused on the synthesis of a precursor of D-fagomine catalyzed by a mutant FSA. The biocatalyst has been immobilized onto several supports: magnetic nanoparticle clusters (mNC), cobalt-chelated agarose (Co-IDA), amino-functionalized agarose (MANA-agarose) and glyoxal-agarose, obtaining a 29.0%, 93.8%, 89.7% and 53.9% of retained activity, respectively. Glyoxal-agarose FSA derivative stood up as the best option for the synthesis of the precursor of D-fagomine due to the high reaction rate, conversion, yield and operational stability achieved. FSA immobilized in glyoxal-agarose could be reused up to 6 reaction cycles reaching a 4-fold improvement in biocatalyst yield compared to the non-immobilized enzyme.

Quantum Dots and Gold Nanoparticles as Scaffolds for Enzymatic Enhancement: Recent Advances and the Influence of Nanoparticle Size

Nanoparticle scaffolds can impart multiple benefits onto immobilized enzymes including enhanced stability, activity, and recoverability. The magnitude of these benefits is modulated by features inherent to the scaffold–enzyme conjugate, amongst which the size of the nanoscaffold itself can be critically important. In this review, we highlight the benefits of enzyme immobilization on nanoparticles and the factors affecting these benefits using quantum dots and gold nanoparticles as representative materials due to their maturity. We then review recent literature on the use of these scaffolds for enzyme immobilization and as a means to dissect the underlying mechanisms. Detailed analysis of the literature suggests that there is a “sweet-spot” for scaffold size and the ratio of immobilized enzyme to scaffold, with smaller scaffolds and lower enzyme:scaffold ratios generally providing higher enzymatic activities. We anticipate that ongoing studies of enzyme immobilization onto nanoscale scaffolds will continue to sharpen our understanding of what gives rise to beneficial characteristics and allow for the next important step, namely, that of translation to large-scale processes that exploit these properties.

Cellulose as a template to fabricate a cellulase-immobilized composite with high bioactivity and reusability

Herein, a new strategy was developed to fabricate an oriented cellulase/chitosan/Fe₃O₄composite, which possesses extremely high activity, reusability, and stability.

In Vitro Metabolic Engineering of Amorpha-4,11-diene Biosynthesis at Enhanced Rate and Specific Yield of Production

In vitro metabolic engineering is an alternative approach to cell-based biosynthesis. It offers unprecedented flexibility for the study of biochemical pathways, thus providing useful information for the rational design and assembly of reaction modules. Herein, we took the advantage of in vitro metabolic engineering to initially gain insight into the regulatory network of a reconstituted amorpha-4,11-diene (AD) synthetic pathway. Guided by lin-log approximation, we rapidly identified the hitherto unrecognized inhibition of adenosine triphosphate (ATP) on both farnesyl pyrophosphate synthase (FPPS) and amorpha-4,11-diene synthase (ADS). Furthermore, the byproduct, pyrophosphate (PPi), potently inhibits ADS, but not FPPS. To lower the inhibition, an ATP recycling system and pyrophosphatase were used and resulted in a significant (∼3-fold) enhancement in the rate of AD production (∼5.7 μmol L^-1 min^-1). A coimmobilized multienzyme reaction system was then developed to recycle the enzymes. When inhibitory metabolites concentrations were reduced, the specific enzymatic yield of AD was further enhanced (>6-fold). This study demonstrated that mitigating the accumulation of inhibitory metabolites can result in higher yields of AD production by in vitro multienzymatic reactions.

Design of nanoscale enzyme complexes based on various scaffolding materials for biomass conversion and immobilization

The utilization of scaffolds for enzyme immobilization involves advanced bionanotechnology applications in biorefinery fields, which can be achieved by optimizing the function of various enzymes. This review presents various current scaffolding techniques based on proteins, microbes and nanomaterials for enzyme immobilization, as well as the impact of these techniques on the biorefinery of lignocellulosic materials. Among them, architectural scaffolds have applied to useful strategies for protein engineering to improve the performance of immobilized enzymes in several industrial and research fields. In complexed enzyme systems that have critical roles in carbon metabolism, scaffolding proteins assemble different proteins in relatively durable configurations and facilitate collaborative protein interactions and functions. Additionally, a microbial strain, combined with designer enzyme complexes, can be applied to the immobilizing scaffold because the in vivo immobilizing technique has several benefits in enzymatic reaction systems related to both synthetic biology and metabolic engineering. Furthermore, with the advent of nanotechnology, nanomaterials possessing ideal physicochemical characteristics, such as mass transfer resistance, specific surface area and efficient enzyme loading, can be applied as novel and interesting scaffolds for enzyme immobilization. Intelligent application of various scaffolds to couple with nanoscale engineering tools and metabolic engineering technology may offer particular benefits in research.

Coupled reactions on bioparticles: Stereoselective reduction with cofactor regeneration on PhaC inclusion bodies

Chiral alcohols are important building blocks for specialty chemicals and pharmaceuticals. The production of chiral alcohols from ketones can be carried out stereo selectively with alcohol dehydrogenases (ADHs). To establish a process for cost-effective enzyme immobilization on solid phase for application in ketone reduction, we used an established enzyme pair consisting of ADH from Rhodococcus erythropolis and formate dehydrogenase (FDH) from Candida boidinii for NADH cofactor regeneration and co-immobilized them on modified poly-p-hydroxybutyrate synthase (PhaC)-inclusion bodies that were recombinantly produced in Escherichia coli cells. After separate production of genetically engineered and recombinantly produced enzymes and particles, cell lysates were combined and enzymes endowed with a Kcoil were captured on the surface of the Ecoil presenting particles due to coiled-coil interaction. Enzyme-loaded particles could be easily purified by centrifugation. Total conversion of 4'-chloroacetophenone to (S)-4-chloro-α-methylbenzyl alcohol could be accomplished using enzyme-loaded particles, catalytic amounts of NAD(+) and formate as substrates for FDH. Chiral GC-MS analysis revealed that immobilized ADH retained enantioselectivity with 99 % enantiomeric excess. In conclusion, this strategy may become a cost-effective alternative to coupled reactions using purified enzymes.

Recombinant CBM-fusion technology - Applications overview

Carbohydrate-binding modules (CBMs) are small components of several enzymes, which present an independent fold and function, and specific carbohydrate-binding activity. Their major function is to bind the enzyme to the substrate enhancing its catalytic activity, especially in the case of insoluble substrates. The immense diversity of CBMs, together with their unique properties, has long raised their attention for many biotechnological applications. Recombinant DNA technology has been used for cloning and characterizing new CBMs. In addition, it has been employed to improve the purity and availability of many CBMs, but mainly, to construct bi-functional CBM-fused proteins for specific applications. This review presents a comprehensive summary of the uses of CBMs recombinantly produced from heterologous organisms, or by the original host, along with the latest advances. Emphasis is given particularly to the applications of recombinant CBM-fusions in: (a) modification of fibers, (b) production, purification and immobilization of recombinant proteins, (c) functionalization of biomaterials and (d) development of microarrays and probes.

Cell-free metabolic engineering: biomanufacturing beyond the cell

Industrial biotechnology and microbial metabolic engineering are poised to help meet the growing demand for sustainable, low-cost commodity chemicals and natural products, yet the fraction of biochemicals amenable to commercial production remains limited. Common problems afflicting the current state-of-the-art include low volumetric productivities, build-up of toxic intermediates or products, and byproduct losses via competing pathways. To overcome these limitations, cell-free metabolic engineering (CFME) is expanding the scope of the traditional bioengineering model by using in vitro ensembles of catalytic proteins prepared from purified enzymes or crude lysates of cells for the production of target products. In recent years, the unprecedented level of control and freedom of design, relative to in vivo systems, has inspired the development of engineering foundations for cell-free systems. These efforts have led to activation of long enzymatic pathways (>8 enzymes), near theoretical conversion yields, productivities greater than 100 mg L(-1) h(-1) , reaction scales of >100 L, and new directions in protein purification, spatial organization, and enzyme stability. In the coming years, CFME will offer exciting opportunities to: (i) debug and optimize biosynthetic pathways; (ii) carry out design-build-test iterations without re-engineering organisms; and (iii) perform molecular transformations when bioconversion yields, productivities, or cellular toxicity limit commercial feasibility.