#16 from R&D Innovator Volume 1, Number 5          December 1992

Learning from Nature
by Saul Neidleman, Ph.D.

Dr. Neidleman is senior director of project acquisition and planning at Biosource Genetics Corporation in Vacaville, California.

The seeds of the jojoba shrub are another item in nature's apothecary, used to produce an oil for many cosmetic formulations.  Because the oil is quite expensive to produce, I set out to find an economical substitute.

I thought a bacterium might prove an economical source of cosmetic oil, because bacteria can produce lipids, and the process can be controlled in a fermentor.  There was only one small problem--we found no reports of bacteria making this particular type of oil.

There is, however, a bacterium called Acinetobacter, which makes a solid wax with many of the properties we wanted in our substitute oil.  Waxes and oils are both lipids, and a great deal is known about how bacteria produce and use lipids.

A Biochemistry Lesson

Digressing momentarily from the jojoba problem, a short biochemistry lesson might be useful.  Lipids with varying properties, are an essential component of the membranes that wrap around living cells.   At any given temperature, some lipids are more liquid and others more waxy:  Lard is solid at room temperature while olive oil is liquid.   

When a bacterium grows in a cold environment, its membrane must be fluid, or oily.  In a warm environment, the membrane must be more rigid, what we call solid or waxy.  If a cell's membrane fails to respond appropriately to temperature changes, its integrity will be disrupted, and it will die.

Fortunately for their purposes and mine, cells respond to temperature changes by altering their chemistry and making different types of lipids.  To convert a wax to an oil, a bacterium removes hydrogen from the lipid.  It adds hydrogen to make the oil more waxy.

Applying That Lesson

Getting back to my surmise:  Could we lower the growing temperature of the Acinetobacter and cause them to answer nature's call and produce an oil rather than a wax?  You wouldn't be reading this unless this surmise succeeded.   Although the organism grows more rapidly at 25˚C, it yields a jojoba-like oil at 15˚C, an unsaturated lipid with fewer hydrogen atoms and therefore greater fluidity.  Thus we took advantage of nature's own adaptive mechanism to "persuade" the bacterium to make the kind of lipid we wanted.

But this was not the end of the project.  We had to modify the chemistry of the oil to bring its properties even closer to those of jojoba oil.  To do this, we had to make sure that we had enough carbon atoms in the oil so it had the correct solubility.  We experimented with changing the number of carbon atoms in the material we fed to the bacteria and which it metabolized into the oil.

Jojoba oil--our goal--contains organic esters with 38 to 44 carbon atoms.  Bacteria biochemically synthesize esters by doubling the number of carbon atoms in the precursor molecule.  Thus, we needed a precursor with approximately 20 carbon atoms, and it turned out that a particular fraction of hydrocarbons from crude oil refining had just the right number of precursor carbons.  Fortunately, this material was inexpensive. 

When Acinetobacter  growing at 15C were fed these 20-carbon precursors, they produced a jojoba-type oil.  So we again allowed nature's know-how and raw materials to influence our product design and production method.

But at that point, our yield was still minuscule, so we used two tacks to increase it.  We found that the bacterium was enzymatically degrading the oil immediately after synthesizing it.  We solved that problem by establishing an aqueous (water) layer and an organic layer in our process chamber.  As quickly as the oil was made, it was extracted into the organic layer, where it was inaccessible to the problem enzyme. 

Once again we took a tip from nature:  Nutrients are often sequestered in an organic phase; that's why an oil slick on the ocean is not available to most organisms in the water.  Although some voracious organisms can attack those nutrients by producing a surfactant to release them from the organic phase, our approach worked because Acinetobacter  had not developed that technique.

Finally, we boosted the yield of lipid with classical mutation methods.  We used ultraviolet light and various chemicals to induce large numbers of mutants and found some that produced much more of the jojoba-like oil than the parent strain.  This method is really the same type of process that nature has been using through countless eons of evolution.  If the natural mutation increases survival rates, nature adopts the process.  In industry, if the artificial mutation increases production of the right materials, companies adopt the mutant. 

As a chemist, I continually look to nature for clues.  Many of my proudest breakthroughs have started with a look at what is taking place in nature.  Nature can be a generous partner to the creative scientist.

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