Computer applications in fermentation

The use of computers for for modelling fermentation processes started in 1960s. Initially the use of computers was restricted because of the cost factor but reductions in the cost and the availability of the cheaper small computers has widened interest in their possible applications. The availability of efficient small computers has led their use for pilot plants and laboratory systems because the financial costs for the online computer systems counts the insignificant part of the whole system. There are three distinct systems areas of computer function postulated by Nyiri in 1972:

a) Logging of Process Data: This is performed by the data acquisition which has both hardware  and software components. there is  an interface between the sensors and the computer. the software should include the computer program for sequential; scanning of the sensor signals and the procedure of data storage.

b) Data Analysis: Data reduction is performed by the data analysis systems which is  acomputer program based on a series of mathematical equations. the analysed information may be put on a print out, fed into data bank or utilized for process control.

c) process control: is also performed by a computer program. signals from the computer are fed tio the pumps, valves or switches via the interface. in addition to this computer program may contain instructions to display devices or teletypes to indicate alrms.

Components of Computer Linked system:

When a computer is linked to a fermenter to operate as a control and recording system, a number of factors must be considered to ensure taht all the components interact  and function satisfactorily for the control a d data logging.An example is DDC (Direct Digital Control) system to explain the computer controlled addition  of a liquid from a resrvoir to a fermenter. 

A simple outline of the main components is as follows:

 

 

Sensor S in fermenter produces a signal which may need to be simplified and conditioned in the correct analogue form. at this stage it is necessary to convert the signal to a digital form which can be  subsequently transmitte dto the computer. An interface is placed in the circuit  at this point. The interface serves as  the junction point for the inputs  from the fermenter  sensors to the computers and output signals  from the computer to the fermenter controls such as  a pump T attached to an additive reservoir.

A sensor will generate  a small voltage proportional to the parameter it is going to measure. for example a temperature probe might generate 1V at 10^oC and 5V at 50^oC. But this signal cannot be understood by the computer  and must be converted  from an analogue to digital converter ( ADC) into digital form.

The accuracy will depend upon the number of bits  it sends to the computer. AN 8-bit converter will work in the range of 0-255 and it is tehrefore  able to divide  a signal voltage into  256 steps. This will give  amaximum accuracy of 100/256, which is pproximately  0.4%. However a 10- bit converter  can give 1024 steps with a n accuracy of 100/1024, which is pproximately 0.1%. therefore when a parameter is to be monitored  very accurately  a converter of the appropraite degree of accuracy will be required. the time taken for an ADC to convert voltage signals to a digital output will vary with accuracy, but improved accuracy will lead to slower conversion  and hence slower control responses. The small computers is often used for one or more fermenters. it is coupled  to a real time clock, which determines how frequently  readings from teh sensor should be taken and possibly recorded. Ancillary equipments  include  a VDU, a data store , a teletype, a graphic display unit, a print out, alarms and barometer.

It is also possible to develop online programs so that online instruments can be checked regularly and recalibrated when necessary.

penicillin production

PENICILLIN PRODUCTION:

Penicillin was the first naturally occurring antibiotic discovered. It is obtained in a number of forms from Penicillium moulds. Penicillin is not a single compound but a group of closely related compounds, all with the same basic ring-like structure (a β-lactam) derived from two amino acids (valine and cysteine) via a tripeptide intermediate. The third amino acid of this tripeptide is replaced by an acyl group (R) and the nature of this acyl group produces specific properties on different types of penicillin.

 There are two different types of penicillin.

Biosynthetic penicillin is natural penicillin that is harvested from the mould itself through fermentation.

Semi-synthetic penicillin includes semi synthetic derivatives of penicillin – like Ampicillin, Penicillin V, Carbenicillin, Oxacillin, Methicillin, etc. These compounds consist of the basic Penicillin structure, but have been purposefully modified chemically by removing the acyl group to leave 6-aminopenicillanic acid and then adding acyl groups that produce new properties.

These modern semi-synthetic penicillins have various specific properties such as resistance to stomach acids so that they can be taken orally, a degree of resistance to penicillinase (or β-lactamase) (a penicillin-destroying enzyme produced by some bacteria) and an extended range of activity against some Gram-negative bacteria. Penicillin G is the most widely used form and the same one we get in a hypodermic form.

PENICILLIN G

Penicillin G is not stable in the presence of acid (acid-labile). Since our stomach has a lot of hydrochloric acid in it (pH2.0), if we were to ingest penicillin G, the compound would be destroyed in our stomach before it could be absorbed into the bloodstream, and would therefore not be any good to us as a treatment for infection somewhere in our body. It is for this reason that penicillin G must be taken by intramuscular injection – to get the compound in our bloodstream, which is not acidic at all. Many of the semi-synthetic penicillins can be taken orally.

Penicillium chrysogenum that produce antibiotics, enzymes or othersecondary metabolites frequently require precursors like purine/pyrimidine bases or organic acids to produce said metabolites. Primary metabolism is the metabolism of energy production for the cell and for its own biosynthesis. Typically, in aerobic organisms (Penicillium chrysogenum) it involves the conversion of sugars such as glucose to pyruvic acid2 and the production of energy via the TCA cycle. Secondary metabolism regards the production of metabolites that are not used in energy production for example penicillin fromPenicillium chrysogenum. In this case the metabolite is being utilized as a defence mechanism against other microorganisms in the environment. In essence Penicillium chrysogenum can kill off the competition to allow itself to propagate efficiently. It should be noted that these secondary metabolites are only produced in times of stress when resources are low and the organism must produce these compounds to kill off its competitors to allow it to survive.

MEDIA FORMULATION:

Lactose: 1%

Calcium Carbonate: 1%

Cornsteep Liquor: 8.5%

Glucose: 1%

Phenyl acetic acid: 0.5g

Sodium hydrogen phosphate: 0.4%

Antifoaming Agent: Vegetable oil

FERMENTATION

To begin the fermentation process, a number of these spores will be introduced into a small (normally 250-500ml) conical flask where it will be incubated for several days. At this stage, explosive growth is the most desired parameter and as such the medium in the flask will contain high amounts of easily utilisable carbon and nitrogen sources, such as starch and corn-steep liquor. At this stage, the spores will begin to revive and form vegetative cells. Temperature is normally maintained at 23-280C and pH at ~6.5, although there may be some changes made to facilitate optimum growth. The flask will often have baffles in it and be on a shaking apparatus to improve oxygen diffusion in the flask.

Once the overall conditions for growth have been established and there is a viable vegetative culture active inside the flask, it will be transferred to a 1 or 2 litre bench-top reactor. This reactor will be fitted with a number of instruments to allow the culture to be better observed than it was in the shake flask. Typical parameters observed include pH, temperature, and stirrer speed and dissolved oxygen concentration. This allows tweaking of the process to occur and difficulties to be examined. For example, there may not be enough oxygen getting to the culture and hence it will be oxygen starved.  At this point, the cells should be showing filamentous morphology, as this is preferred for penicillin production. As before, cell growth is priority at this stage. At this stage, growth will continue as before, however, there are often sudden changes or loss in performance. This can be due to changes in the morphology of the culture (Penicillium chrysogenum is a filamentous fungi and hence pseudoplastic) that may or may not be correctable.

At this stage the medium being added to the reactor will change. Carbon and nitrogen will be added sparingly alongside precursor molecules for penicillin fed-batch style. Another note is that the presence of penicillin in the reactor is itself inhibitory to the production of penicillin. Therefore, we must have an efficient method for the removal of this product and to maintain constant volume in the reactor. Other systems, such as cooling water supply, must also be considered. If all goes well we should have penicillin ready for downstream processing. From here it can be refined and packaged for marketing and distribution to a global market.

References:

1. Hare, T; White, L / penicillin production

2.http://nobelprize.org/medicine/educational/penicillin/readmore.html