E. coli, the green celebrity!

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Geralt

Escherichia coli or more commonly known as E. coli, according to me, happens to be the celebrity of the green world when it comes to biology in green chemistry. These are the friendly bacteria that live in our guts and help digest our food. Although, some of its strain do cause problems to us. It’s time to give it some positive attention. Scientists genetically engineer E. coli and greenify a chemical reaction.

Here are a few examples of how they did it:

  1. Reduction of GO: Microbial reduction of graphene oxide by Escherichia coli: A green chemistry approach
  2. Cleaner chemistry: Transplanting metabolic pathways into E. coli
  3. Biofuels: Turning bacteria into butanol biofuel factories
  4. Turning waste into fatty acids: Genetically Modified E. coli Bacteria Turn Waste Into Fat For Fuel!
  5. Sugars into biofuels

The Presidential Green Chemistry Challenge Award Recipients included individuals/organizations who used E. coli. Here are some entries:

2012 Codexis, Inc.; Professor Yi Tang, University of California, Los Angeles LovD, an acyltransferase from E. coli engineered by directed evolution, now performs regioselective acylation in the sysnthesis of the drug simvastatin (summary)
2011 BioAmber, Inc. Genetically engineered E. coli strain licensed from the Department of Energy produces succinic acid from wheat-derived glucose on a commercial scale (summary)
2011 Genomatica Genetically engineered E. coli strain produces 1,4-butanediol by fermentation of readily available sugars (summary)
2011 BioAmber,Inc. Glucose is fermented on a commercial scale by a genetically engineered E. coli strain to make succinic acid, traditionally produced from petroleum (summary)
2011 Genomatica Readily available sugars fermented by a genetically engineered E. colistrain produce 1,4-butanediol, a large-volume chemical usually made from petroleum (summary)

The world outside our guts is far harsher for these bacteria, especially in our reaction flasks. So what are scientists doing about it? They are making hospitable environments for these little celebrities. Making safer solvents for them is one way. But is E. coli losing its shine? Time will tell.

Read more:

How yeast replaced E. coli: BioAmber phases out E.coli use

Indian Dyestuff Industry

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Most of these industries are batch processes. These industries produce around 90,000 tons of dyes, out of which 10% is exported. Covering coastal areas of Maharashtra and Gujarat, these industries are located majorly in the belt of Ahmedabad to Chiplun. Coastal areas are preferred since these processes are water-intensive.

industries

Other than water, the most common substance used in the dye industry is common salt. Why is this common salt a concern to us? Common salt if present in huge amounts in the effluent of these industries, can render good land to a barren one. Not to mention its corrosive power.

The E-factor of this industry is 50.

The total world market for dyes is a whooping 7 billion with a 2% growth rate. This growth rate is highly evident in populated nations like Asia. Dystar is one of the largest manufacturers of dyes.

Like any other industry, the dye industry faces issues like:

  • water pollution
  • air pollution
  • land pollution
  • waste management
  • health and safety

In places like Ankaleshwar, Mahad, Parshuram, some parts of Dombivali, air pollution in monsoon is highly visible. For a person with asthma, these places can prove fatal. It is not just India, but China too, both have profound demographics.

So, what is the world doing about this?

Read more about how companies like the ones below, are developing green technologies to tackle water abuse in this article.

airdye

Water filtration by tomato and apple peels

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In order to enhance the ability of apple peels towards extraction of negatively charged pollutants, Mr Ramakrishna immobilised naturally occurring zirconium oxides onto the surface of apple peels. Zirconium loaded apple peels were found to be able to extract anions such as phosphate, arsenate, arsenite, and chromate ions from aqueous solutions.

Read more:  NUS researchers developed world’s first water treatment techniques using apple and tomato peels

Solar for elec…naah, heat!

“Utilization ratios — the proportion of solar radiation reaching a collector’s surface that can be converted to usable process energy — of over 60% can be obtained by integrating solar thermal equipment in industrial systems. By comparison, photovoltaic systems typically have an efficiency of around 15%. ” –che.com

Solar energy can not only be transformed into electricity, but process heat in a chemical industry.

Read more on this : Producing Solar Process Heat with Fresnel Collectors in the CPI

Converting solar energy into heat is not new. Solar cooking is one such application.

The world’s largest solar cooking system, designed by Gadhia Solar Energy Systems Pvt. Ltd., is functioning at the Shirdi temple, where a solar cooked lunch is served to over 50,000 people per day.

It is not just India, but this technology is used worldwide.

Read more:

Most significant solar cooking projects

Edit (13/09/2013)

Nanoheaters really boggled my mind the most.

“Nanoheaters generate steam at a remarkably high efficiency,” Halas said. “More than 80 percent of the energy they absorb from sunlight goes into production of steam. In the conventional production of steam, you would have to heat the entire container of water until it boils, with the bubbles rising to the top to release steam. With nanoheaters, less than 20 percent of the energy heats the neighboring liquid.”

Read more: New Solar Device Kills Germs on Surgical Equipment (and Everything Else)

Green chemistry and catalysis

Catalysis helps us:

  • reduce reaction time, which in turn saves energy
  • selectively carry out parallel reactions, which again saves time and money required for separation of the side-products. Some side-products are harmful and dangerous. So it also keeps us safe.
  • replace stoichiometric reagents with catalytic amounts of a substance, which helps us save resources and money. Some stoichiometric reagents are harmful and also create problems due to its existence. For example, aluminum chloride is a reagent used in Friedel–Crafts reaction, is a highly corrosive substance and also ends up acidifying the waste stream. Separation of AlCl3 is lengthy and expensive and it cannot be recycled due to its corrosive nature. A greener alternative for this can be explained with an example. Catalytically effective amount of a mixture of bismuth tri-halide and of perfluoroalkanesulfonic acid can be used for sulfonation reactions instead of AlCl3.

By and large, catalysts are a way to make a reaction go green. But, if one can find a way to turn a reaction greener without using a catalyst, even better. How can one do that? Alternative energy options such as microwave and ultrasound often can help us carry out reactions without using a catalyst or a solvent.

Ionic liquids are a fairly new class of catalysts. A part of the research community is cautious about using them as catalysts. Even though they are non-volatile unlike common solvents, they can be hazardous. From cradle to grave approach, that is from synthesis to its disposal, these can prove to be extremely harmful to us and the environment. Are they?

Read more:

Ionic liquids: green or not green?

Thermal Safety of Ionic Liquids

What the industry needs

What is needed for an industrial catalyst?

  1. High stability
  2. High selectivity
  3. Activity
  4. Ease of availability

I did not say high activity, since the kind of activity needed depends on the application. A highly active catalyst can affect the selectivity. Also, if the activity is lower than needed, it can be elevated using promoters.

A catalysts loses all this due to the following reasons:

  1. Poisoning
  2. Coking
  3. Decomposition

Catalysts if reusable, can undergo wear and tear due to the above mentioned reasons. Poisoning can occur due to impurities in the product streams, or the products itself can poison it. Sulfur is a notorious catalyst poison. It haunts the petroleum industry. It bonds to the active sites of the catalyst. Oxygen and water, are catalysts poisons for iron catalyst in ammonia synthesis.

Selective poisoning is deliberate poisoning of highly active catalysts that are so active that they catalyze undesired side reactions. Lindlar’s catalyst is one such example. Lindlar’s catalyst is a palladium catalyst poisoned with traces of lead and quinoline, that reduce its activity such that it can only reduce alkynes, not alkenes.

Coke is what gets deposited on a catalyst during oil refining. It deactivates it. The catalyst can be reactivated by burning it off.

Catalyst deactivation due to coke formation is an important technological and economic problem in petroleum refining and in the petrochemical industry. Remedies to catalyst deactivation are sought by a variety of strategies involving modification of catalyst surface composition such as the use of polymetallic catalysts and/or by manipulation of the reaction environment which often limits the yield due to thermodynamic constrains (i.e., high hydrogen pressures, etc.). In the limit, when the activity reaches unacceptable limits, regeneration by burning off carbon residues can usually be attained, Regeneration can take place in situ, as in fixed-bed reactors, or in an adjacent reactor to which the catalysts is transported to, such as in moving-bed reactors or in fluidized-bed reactors. In the first case intermittent operation is required, whereas in the second case the operation is continuous, but a second regeneration reactor is required. The choice of the proper process cycle is an economic optimization problem constrained by catalysts cost, operational and regenerational cost, and by the value of the final product [1–5]. Process optimization under catalyst decay is an engineering problem that requires a knowledge of the catalyst deactivation kinetic. – E. E. Wolf & F. Alfani, Catalysis Reviews: Science and Engineering, Volume 24, Issue 3, 1982

Decomposition of a catalyst occurs when it is exposed to temperatures it cannot handle. It renders it thermally, structurally and chemically unstable.

deactivation

Deactivation mechanisms: A) Coke formation, B) Poisoning, C) Sintering of the active metal particles, and D) Sintering and solid-solid phase transitions of the washcoat and encapsulation of active metal particles (cf. Suhonen 2002).

(Image: Oulu University Library)

Although regenerating a catalyst brings it back to life, but in due course it keeps losing its activity bit by bit if not entirely, which is when it is eventually replaced. A catalyst, like diamond, is not forever. The worth of the catalyst can be found by knowing its TOF and TON.

TOF is its turn over frequency and TON is its turn over number.

TOF is the amount of reactions per unit time occurring at the reaction center.

TON is TOF upto the death of the catalyst, which can be shown numerically as follows:

TON = TOF * lifetime of the catalyst