CHOOSING THE RIGHT STIRRER

One of the most fundamental requirements in any type of fermentor is the provision of a device or mechanism to mix the contents of the fermentor. Good mixing will result in homogenous conditions of the fermentation broth which will help improve good mass transfer leading to an efficient fermentation process.
It is therefore not surprising to see in fermentors the provision of a stirrer or some sort of mixing device to execute this important function. Good mixing is not only restricted in liquid fermentation but also in solid substrate fermentation such as cocoa fermentation and even composting.
Many of us are so ingrained by the ‘brainwashing’ of fermentation literature that a standard fermentor is and always must be accompanied by a standard mixing device such as the motor, shaft and impeller combination. To this influence we are also brainwashed that Rushton turbine is the ‘best’ impeller system. Due to this also we dare not think ‘outside the box’ and are happily satisfied with the standard Rushton turbine despite the fact that the kind of fermentation we are using is not the same as those reported for the standard stirrer. Part of the blame for this ignorance is to be blamed on the users for failing to understand themselves the kind of fermentation they are carrying out, their limitations and failing to appreciate the rheology of their own broth.
The only exceptions to this poor thinking which I observed are those involved in disposable bag reactors and those dealing with the cultivation of plant and mammalian cells. In plant cell cultivation the mixing is brought about by the circulation of the fine air bubbles. In the disposable bag fermentation they use gentle waves which help in the mixing of the fermentation broth.
In the market there are various types of stirrers, shafts and impellers. You must be able to choose the right combination for your purpose.
In this aspects it is important that we need to know :
1 What sort of fermentation are we carrying out?
2 What is the size and geometry of the fermentor
3 The rheology of the fermentation broth
4 The kind of flow we expect for the fermentation
It is only after we have considered the above we custom fit the stirring configurations.
The type of flow generated by the stirrer is important. It is easy to get laminar flow or even non laminar flow for Newtonian rheology. Things do becomes complex if the fermentation broth which we are dealing are of the Non Newtonian type. In certain cases, the types of Non Newtonian transformations become even more complex.

The choice of the proper stirrer will have to be seen from:
1 The shaft component
2 The blades or the impellers
If we are dealing with viscous fermentation broth it is advisable we use shafts with bigger diameter. The length of the shaft too is critical to the efficiency of the shaft
The choice of the type of blades will determine if the flow produced will be radial or axial. Propeller stirrer shaft will produce axial flows. Which will result the flow moving away from the shaft? The inclination or direction in change of rotation will have impact on the direction of the flow
In cases where the blades are arranged on the disc will have flow attributes which will show strong shearing properties. The flow will be radial and directed outwards. Such flow will generate strong axial suction ia top and bottom axis
Impeller stirrer shaft will provide strong radial flows .
There are the so called anchor design stirrers with the shaft fitting in the centre of a “U” shape structure. This effective in generating tangential flows but poor axial forces or movement of the fermentation broth
There are also hybrid stirrers where both type of propeller blades and impeller blades share the same shaft. Usually the propeller blade is located at the top to induce downward flow to the blades with radial flows
It is important therefore in decoding the choice of stirrers the user must understand the rheology and viscosity of their fermentation broth before rushing like a fool to carry out just any fermentation using the ‘standard stirrer’ The best part of these fermentation studies not only they will not be able to determine the optimal fermentation conditions for their fermentation study but they have faith in “ stupid data’ their studies generated.
I just love the way the fools rushed in where angels fear to tread.. Read more!

RELEVANCE OF REYNOLD’S NUMBER IN FERMENTATION TECHNOLOGY

I personally think that there is too much of irrelevant engineering in fermentation technology. The obsession with mathematical equations, models by engineers into fermentation technology just add further to the mysticism of fermentation. It only helps in making the subject of fermentation technology so esoteric and beyond the reach and understanding of most people including the engineers themselves. After all, the abuse of irrelevant engineering and mathematics only serve in trying to make “sense” out of “non sense”. The logic is simple enough. How can you ever claim to control and optimize the fermentation process if you have very little understanding of the variability of the process?
Yes! Such mathematical and engineering studies and experiments will still data or rather “erroneous data” which one can still try to make some sense out of it. The end product will yield wrong and erroneous conclusions. At this point I am not saying that all the engineering or mathematical input are useless or irrelevant.
The trouble is there is a persistent and irritating trend by chemical engineers and biochemical engineers trying to justify their intrusion into the field of fermentation technology and not vice versa! Good examples are the adoption of unit processes in downstream processing. In a feeble bid trying to improve the engineering or mathematical input into fermentation technology they even try to apply Monod’s equation, Lineweaver Burke into the fermentation modeling! How relevant or significant input these contributions are is another question.
We are thankful for the engineers in helping build or design the fermentors we have on the market now. But looking with perspective over time we see there is no real significant development or advancement in the design and structure of fermentors from the days of Fleming industrial production of penicillin. What we are having now are in fact “living fossils” of the old antiquated fermentors. Nothing much has really changed!
Let us look at the application and relevance of Reynold’s Number to fermentation technology.
Historically, the exposition of Reynold’s Number is the keystone to fluid mechanics. It is more and observation on the nature of fluid flow which includes air and liquid such as observed in wind tunnel, aerodynamics and in trying to explain the transformation of simple laminar flow to complex flow turbulence
The application of Reynolds number might be of relevance in aerodynamics of flight where it is necessary to understand the behavior of objects exposed to high speed wind velocity and turbulence. But I cannot really see the relevance of Reynolds Number at the level of fermentor where we are really dealing at low rpm. In fact, laminar flow is not really sought after in fermentor as turbulence is needed to improve the various mass transfer processes during fermentation
To complicate things further the behavior of the fermentation broth is complex in terms of its phases and changes that occur as a function of time. The rheology of the fermentation broth is complex and almost no two fermentation broth are the same. In fact there are so many variables involve which will influence the Reynolds number such as size, geometry, broth type, media composition and even the composition of microorganisms used in the fermentation process
There for do we really need to apply Reynolds Number in the study of fermentation process or is it just a vestigial reminder left by the engineers for us just like the mysterious smile of the sphinx?

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Ave Atque Vale there's a time and place for everything. The place is here. I just need to find the right time.

(THE FOLLOWING ARTICLE WAS TAKEN FROM THE ABOVE BLOG WITHOUT PERMISSION)
Something to ponder....


Sunday, September 5, 2010
I am...
I am a Malaysian.

With that notion firmly entrenched, I bear witness that my country is now 53 years old. It was an age ripened from the valiant efforts of yesteryears’ soldiers who fought for our country’s independence from both internal forces and foreign masters. Though many lost their lives (and are now remembered in memorials such as God’s Little Acre in Batu Gajah or honoured during Warriors Day), the nation was really one in uniting against the perils of communist and rejoicing together when the Union Jack was lowered many years ago. The Malayans simply lived together as religious and racial differences were assimilated to celebrate independence.

Now, Malaysia is an independent nation and unfortunately, the same ‘independence’ has lost its value. While we no longer have to survive communism or colonialism, we are struggling against new evils that were never there. There is a worrying trend of rising racism and religious intolerance between the different races in Malaysia, no doubt fuelled by unscrupulous parties out to serve their own causes. At the same time, we have leaders who preached about ‘Vision 2020’, ‘Malaysia Boleh’, ‘Cemerlang, Gemilang, Terbilang’ and the latest to join the bandwagon is to point one finger upward and utter ‘One Malaysia’.

I am perturbed by how we’re defined by what our leaders label us to be. Far more amusing is that we allow these linguists, the opportunities to ‘reinvent’ Malaysia time and time again when everybody knows the main problem remains unsolved.

Vision 2020 is fast approaching and Malaysia is nowhere near the intended aim of becoming a first world developed nation. Well, if having the KLIA and hosting the Sepang Grand Prix once a year are the cornerstones of a developed nation, then hooray for us. And perhaps Vision 2010 was also dreamt for moments when we burst with pride that our local universities managed to be in the top 200 universities in the world ranking, one that befits our country’s aim of becoming the region’s top education hub. After all, it’s definitely none of our business that neighbouring countries’ universities are mostly ranked in the top 50! Our consolation (and we’re great at finding excuses) could be in the well known story of the hare and tortoise where the tortoise will eventually win. The problem is, we were actually the hare back in those days when our premier university was racing together with NUS, side-by-side.

What the education system in Malaysia today is, at best, one of a handicapped tortoise. We’re handicapped in every sense of the word, from graduates who can’t string a perfect sentence in English to educators who treat teaching with much passion as a toothache. But don’t let that dampen our spirits as we have thousands of graduates jamming the job market! Seriously, Malaysians are really lucky because we must be the only country where students are treated as the shuttlecock in changing the medium of instruction from English to Bahasa at one’s whim and fancy. And because what could be the next smart move to abolish national examinations in place of ‘assessments’, everyone will probably be assessed as smart because now, everybody gets to enter university. If you’re unable to enter one of the many local universities (I think at last count, there was 17), one can always go to the countless private universities mushrooming in every nook and cranny. It’s your choice whether you want to opt for an internationally branded private university or an education institution located on the first floor of a shop lot. If you’re undecided in pursuing which course to take, there is no need to seek out professional advice. Just read the stacks of brochures hurled at our doorsteps promoting quality education for all (but please excuse their glaring grammatical errors and suspicious contact numbers). Finally, Vision 2020 is also envisaged for the nation’s youngsters to grow up as borrowers (and eventual defaulters) as education loans are readily and easily available. It is indeed a bargain to borrow thousands of Ringgit for a degree that could be, in most cases, not even worth the paper they’re printed on.

Further, who could blame us for reveling in Malaysia Boleh when we won a handful of medals back in the 1998’s Commonwealth Games? We were the proud hosts, eager to show that Malaysia is able to stand in the eyes of the world. Okay, so we hosted but what were the costs involved again? I do not believe the accounts have been tabled for the citizens to see just how much the nation has spent for vanity’s sake. And yes, Thomas Cup belonged to us back in 1992. That was the Malaysia Boleh moment that saw every Malaysian kid picking up the racquet and shuttlecock in their bid to be the next Sidek brothers. But it is now 2010 and 5 successive campaigns have passed without the Cup in our possession.
Malaysia Boleh could probably be the explanation why the old Subang International Airport (an important building in our country’s history) was demolished to build, and this was a shocking surprise, another airport! Well, it’s now named as some sort of Sky Park but hey, Malaysia Boleh spend okay. Other governments think thrice and scrimp to get money but let us show you the way. Boleh demolish, boleh build, vice-versa. Either way, money will line certain already well-lined pockets.

Then there’s Cemerlang, Gemilang, Terbilang. Honestly, I do not even know the meaning of those words. Perhaps it is ‘cemerlang’ that it only took our fifth prime minister a few years in office before retiring. One should really consider the previous prime minister’s tenure (and my God, he could almost rival the reign of Soeharto or if he’s a royal, the revered King Bhumibol of Thailand or English Queen Victoria). Well, most of us viewed the fourth prime minister’s reign as a regime anyway. It could also be ‘gemilang’ that government officers were directed to wear ‘batik’ every 1st and 15th of the month. I may not be fashionably inclined but who will actually do serious work when one is dressed up for a reception? I am lost for words in considering ‘terbilang’. I’m taking a shot here but has it got anything to do with the number of shrimps hurled to court for allegations of graft and corruption? Or maybe it refers to the lobsters tiding their sunset years with huge mounts of cash in Swiss banks, happy in the thought that lady justice will not be catching up on them anytime soon.

Finally, the ideals of ‘1 Malaysia’. I would be driving on highways and I’m forced to read huge billboards stating ‘1 Impian, 1 Harapan, 1 Malaysia’. The thing that struck my curiosity is this. Why the need to brand ourselves as 1 Malaysia? My grandparents and parents experienced a life made complete with their friends of different races. Sure, they worshipped different gods but they were united in friendship that transcended the influences of masjid, church or temple. They had no need to use separate tables, hang out in racially defined groups or view each other in a hateful manner. There were no assaults just because the other person belongs to a different race. Most importantly, there was never the despicable need to shout at someone to ‘balik Tongsan, China, India’ or wherever that our ancestors came from. And yet, those are the very things happening now under ‘1 Malaysia’. Isn’t it ironic and downright absurd to claim 1 Malaysia when racial intolerance has permeated into the social fabric of the Malaysian society?

I am deeply disgusted that a school principal uttered derogatory remarks about our friends of the Chinese heritage. I am more appalled that one race is seen to be protected more than the rest when it should be that all must be protected under the flag. I am saddened that May 13 happened (though there exists an irritating doubt that what I learnt from the history books are formulated truths) but enough is enough. It is time that we need to exist as Malaysians without any labels. By strict definition, I consider myself a Malay-Chinese Malaysian (given my mixed heritage) but I will not, at any time support racial extremists who see Malaysia as part of their God-given land. Nor will I condone any calls asking my Chinese and Indian friends to return elsewhere for I would need to go with them as well.

We are all here on borrowed time and the land where ‘tumpahnya darahku’ belongs either to all of us or none at all. Happy 53rd Merdeka and a wish for the upcoming 1st Malaysia Day.
Written by Raja Syarafina RS at 10:47 PM 0 hand prints to be shared
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MY APOLOGIES TO READERS

I am very sorry for not being able to continue writing fermentation technology articles for some period of time as I am currently too busy with some projects
Will continue once the hectic phase is gone. My apologies again
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REHABILITATION OF SUNGAI KLANG- AN EXERCISE IN FUTILITY?

What I gather from the newspapers it is going to be a major project that will swallow billions of RM and carried out over 15 years!! Is it going to be more a pipe dream or a reality? Can the project be guaranteed to be successful or is it going to be more money thrown into the polluted river? 15 years is a very long time…. Wonder if the guarantee if any will hold.
One of the most common erroneous assumption is that if the technology was successful for Thames or for the matter the mighty river Han, it does not mean it will be successfully applied for Sg Klang. (Maybe all the parties concerned have their own expert consultants to vouch that every thing will be ok! As for me it is far better to be realistic and prudent. The River Klang is very complex and have many problems. I for one would like to be proven that the project will work…
Would it not be better if the companies concerned are tested first for their ability by giving certain stretches of the rivers to be handled and their performance monitored? To me it is very logical that if the company cannot manage a small portion of the river, it will be questionable if they can rehabilitate the whole stretch of the rivers.
I would love to see the spirit of competition vying with one another in the race to rehabilitate the stretch of rivers given to them. Nothing could be more wrong if all the companies awarded are working in the same group. That is the reason why I like how the Petronas tenders are being awarded, with the Japanese and Koreans competing with each other to complete their own respective towers!
Rehabilitating the Klang river requires more than just mechanical equipment to remove trash or solid wastes. It is more than just building treatment plants along the river. The solution is complex and requires social engineering too. If not we will be back to square one after billions of RM has been pumped into the project.
I for one would not like to see the rehabilitation of Klang river as a very costly exercise in futility!


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INDUSTRIAL PRODUCTION OF ENZYMES: PART 2 PRODUCING MICROBIAL ENZYMES USING FERMENTATION TECHNOLOGY

Fermentation technology has been used extensively in the production of microbial enzymes. There are three main objectives in the production of enzymes using microbes:
1 The enzymes must be produced in high volume
2 The enzymes must be pure
3 The enzymes must be stable especially with respect to its structure and functions

The key element in the production of enzymes using fermentation technology is:
1 The presence of microorganisms which have the capability of producing the desired enzymes
2 The choice of suitable bioreactors or fermentors that can be used to support the cultivation of the microorganisms that produce the enzymes
3 The optimum conditions, control and monitoring of the fermentation conditions for maximum enzyme production
In all the above the nature of the enzymes being produced are often the restricting factors in the production of the enzymes. The main problems are enzymes are basically large complex protein molecules which are not stable and easily denatured by certain extreme conditions such as temperature, salt, ph and other factors.
The production of the enzymes by the microbes are basically a physiological or metabolic function of the microbial cells and factors such as feedbacks and catabolite repression or metabolic inhibition will affect the process
THE PRODUCTION METHOD
The production method of these enzymes is governed primarily by location of the enzymes in the cell and whether the enzymes are inductive or constitutive by nature. Most industries that produce large volumes of enzymes are often involved in inductive enzymes. In such situations there is no need to break the cells or organelles to release the enzymes. As constitutive enzymes are sort of “part of the cell” the amount of enzymes are directly related to the amount of cells produced. In such situations it shows primary metabolites behavior and the growth curve is used to determine the right time to harvest the cells and the constitutive enzymes
In the case of inductive enzymes the process of producing enzymes is simpler. Enzymes that are produced are easily released off the cell into the fermentation media. However, in this method the presents of the substrate or inducer in the media in important to trigger the enzymes production.







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SUNGAI WAY RIVER REHABILITATION PROJECT

I happened to chance upon the studies on the rehabilitation of Sg Way River project. While the intention to take care of the river is noble, it is of utmost importance that such studies be carried out properly in proper scientific manner. Proper samplings, analyses and interpretation of the results must be carried out for the study to be meaningful.
In order for the study to be meaningful goes far beyond than just taking a few random samples from a few sampling stations along the river. Remember, the results obtained from the few samplings might be valid only for the samples taken but they could not be used to extrapolate to the water quality of the river itself (unless one can guarantee that the composition of the river is homogenous and does not change spatially or temporally)
I am a bit disturbed by the way the sampling plan were carried out ( if there were any?) In my opinion the number of sampling stations is too few in number and too far apart. Determining the number and location of the sampling stations are critical to the success of the study. Prior studies must be carried out on the flow and hydrodynamics of the river in order to come up with the most suitable locations that can yield representative samples of the river water.
Sampling is a science and not determined by the convenience of the samplers such as taking samples from the sides of the embankments! Proper sampling utensils or apparatus must be provided to obtain the proper samples. There are many more other considerations which must be considered….

For the complete data please refer to:http://www.waterproject.net.my/index.cfm?&menuid=15

With such few sampling stations, samples, the whole exercise would just remain as a feeble attempt in efforts trying to rehabilitate the river. In my opinion it would have been more proper if the study carried out over the stretch of the driver:
1 Identify the various point source or diffuse source of pollution into the river
2 measure the total maximum daily load from each source
Auditings like this will not only identify the stake holders but also the responsible polluters. It is sad that sometimes the innocent stake holders will have to do the cleaning up of the river while the polluters go away scot free!
I am very disturbed too by the interpretation of the water analyses as provided by the report especially with reference to the Dissolved oxygen, BOD and COD readings. The BOD readings for the three stations W1, W2 and W3 are 5, 4 and 10 mg’litre. Wow! Something is not right here. At such low BOD values the water of Sg Way river is clean and not polluted at all. ( But my eyes see the river as very polluted!) Unless something is wrong or inaccurate in the samples or analyses





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