Biocatalysis

Novozymes, the largest and IMHO best enzyme maker on the planet, has just introduced another innovation. It is called GH-61, which tells you nothing about what it really is. Novozymes calls it an “enzyme booster” that turbocharges the enzymatic degradation of cellulose. Imagine: an additive that boosts the performance of Novozyme’s already high-performing cellulases. Accelerating the conversion of waste cellulosic raw materials–things like corn cobs, straw, corn stalks, sugar cane bagasse (the stalks left over after the sugar has been crushed out), and the like– into sugars that can be fermented to produce biofuels is step forward on the path toward more plentiful and less expensive biofuels.

Commercialization has just been initiated, and sales are only beginning. But CEO Steen Riisgard says: “We are a real company, and when we say we are ready, we mean we are ready.”

I believe him.

“I foresee the day when physiological chemistry will not only make use of the natural enzymes as agents, but when it will also prepare synthetic ferments for its purposes.”

Emil Fischer, Nobel Lecture, 1902

Frances Arnold’s group at the California Institute of Technology (Caltech) and gene-synthesis company DNA2.0 have reported the construction of 15 new highly stable fungal enzyme catalysts that efficiently break down cellulose into sugars at high temperatures. Previously, fewer than 10 such fungal cellobiohydrolase II enzymes were known. In addition to their remarkable stabilities, Arnold’s enzymes degrade cellulose over a wide range of conditions.

Thermostability is a requirement of efficient cellulases, because at higher temperatures–say, 70 or even 80 degrees Celsius–chemical reactions are more rapid. In addition, cellulose swells at higher temperatures, which makes it easier to break down. Unfortunately, the known cellulases from nature typically won’t function at temperatures higher than about 50 degrees Celsius.

“Enzymes that are highly thermostable also tend to last for a long time, even at lower temperatures,” Arnold says. “And, longer-lasting enzymes break down more cellulose, leading to lower cost.”

“This is a really nice demonstration of the power of synthetic biology,” Arnold says. “You can rapidly generate novel, interesting biological materials in the laboratory, and you don’t have to rely on what you find in nature. We just emailed DNA2.0 sequences based on what we pulled out of a database and our recombination design, and they synthesized the DNA. We never had to go to any organism to get them. We never touched a fungus.”

See the full press release here.

Onyx Scientific Ltd, Cyprotex Discovery Ltd and Glytech, a University of York Centre for Novel Agricultural Products spin-out, have formed a unique 3-way collaboration to offer new drug metabolite identification and synthesis services to the pharmaceutical industry.
All 3 organisations contribute separate skills needed in performing this service. Onyx provides synthetic and analytical chemistry services; Cyprotex contributes in vitro screening services, metabolite profiling and identification expertise; Glytech supplies proprietary enzyme screening and bioprocessing skills providing the capability to rapidly make novel metabolite structures.

According to the companies, no single entity in the world is capable of matching this novel approach. That statement sounds a bit too strong to me, but it does add competition to a field that includes Albany Molecular Research (AMRI), Cypex, Xenotech, SPI-BIO (France) and Codexis (via BioCatalytics).

The Journal Chem. Comm. just designated a scientific paper by Nicholas Turner, Matthew Truppo, and J. David Rozzell (Hey, that’s me!) as a Hot Article.  The communication describes a two-enzyme system for producing enantiomerically-pure amines, something which is difficult to do by other means. The link is here. The reaction sheme is below for those chemically inclined.

OK, I know it’s a shameless plug.

The Applied Biocatalysis Center at based at the Technical University of Graz, Austria maintains one of the largest research efforts directed toward biocatalysis. Funded as a Competence Center (Kompetenzzentrum), or K+ Center in Austria, the research efforts have already resulted in a number of biocatalysis successes. DSM, in particular has funded significant projects, including work to clone, express and optimize hydroxynitrile lyase enzymes for chiral cyanohydrin synthesis, and the cloning and first successful expression of pig liver esterase in commercially significant amounts. The Center also maintains a good web site: A-B Graz

Ever wished you could find out how a compound could be degraded or biosynthesized? A great resource to help answer this questions is the U of  Minnesota Biocatalysis/Biodegradation Database, compiled and regularly updated by Prof. Larry Wackett and colleagues. IT contains 182 pathways, 1269 reactions, 177 compounds, 821 enzymes, 479 microorganism entries, and more. This is a great resource, and we will include it in our growing list of resources and link to it here.

It is important to point out that biocatalysis is not a panacea, and I say this as an evangelist for biocatalysis. There are both pros and cons for the use of biocatalysis as compared to more traditional chemical catalysis. As a catalyst, a biocatalyst does what any catalyst can do: increases the rate at which a chemical reaction takes place, but does not affect the thermodynamics of the reaction. To take maximum advantage of biocatalysis, we need to understand what biocatalysts do well, and equally what they do poorly, and then seek to implement biocatalysts in processes that benefit from their advantages.

One of the most important advantages of biocatalysts is high selectivity, manifested as stereo-selectivity (for chiral synthesis or separation, often used for the synthesis of pharmaceutical intermediates in which only one stereoisomer possessesthe desired biological activity), positional selectivity (also known as regio-selectivity, allowing selective modification of a specific site in a molecule), and functional group selectivity (i.e. chemo-selectivity, allowing one type of chemical functional group to be modified in the presence of another, sometimes more reactive functional group). Such selectivity is highly desirable in chemical synthesis, offering benefits such as higher yields, fewer side reactions, elimination of protection and de-protection steps, purer products, easier recovery and separation, and reduced environmental waste. There are also operational advantages, including the ability to carry out reactions under mild operational conditions, avoiding extremes of pH, temperature, and pressure that often require the use of expensive equipment or energy intensive processing. Biocatalytic processes also rely on catalysts that are biodegradable and are produced from renewable resources, meaning the processes are typically “greener” and more sustainable. Since there is an enzymatic counterpart to most known chemical reactions, the potential scope for the application of biocatalysis is broad.

Practically speaking, however, this breadth of scope in the chemical industry has not been realized. Presently, I estimate that well over 100 different biocatalytic processes are implemented in pharmaceutical, chemical, agricultural, and food industries, which may at first glance seem considerable. However, this represents only a small fraction of the processes developed and carried out currently. Enzymes have not yet been developed to cover as broad a spectrum of chemical reactions as have chemo-catalysts. Researchers in both academia and companies are working to overcome this limitation, but it will take time. Speed of process development is also often slower for biocatalytic processes than their chemical counterparts, in part due to the lack of experience that chemists have with the use of enzymes and microbial cells. Modern biotechnological tools now allow enzymes to be significantly improved—optimized—for a desired reaction, but this optimization is often too costly and time-consuming to meet tight timelines; therefore, broad application remains elusive. By focusing on those reactions where enzymatic alternatives are relatively well-developed now, honing our expertise in using biocatalysis, and staying abreast of future developments that will bring a wider range of practical biocatalytic alternatives, we can choose wisely where to invest resources to maximize the value of this rapidly developing technology. 

A good place to start is with definitions, to provide clarity about our subject.

Biocatalysis can be defined as the use of natural substances, which can be one or more enzymes or cells, living, dormant, or dead, to catalyze a chemical reaction or series of chemical reactions. Thus, biocatalysis includes the one-step enzymatic conversion of fumarate to aspartic acid (a component of the non-caloric sweetener aspartame), the two-step oxidation of ethanol to acetic acid (vinegar can be made this way), and the multi-step brewing of beer (quite likely the oldest example of biocatalysis, with historical records dating back 6000 years!).

A biocatalyst, then, is a natural substance, being an enzyme, cell, or a group of enzymes or cells catalyzing a chemical reaction or series of chemical reactions.

As we add content to this site, we will focus on the biocatalyst products available, their applications, their advantages, and the sources of those biocatalyst products, which may be both companies and academic institutions. We might even get opinionated!