Screening of Micro-organism for Industrial Use

Screening of Micro-organism for Industrial Use

The micro-organism that is required in industries are screened or we can say isolated from nature.The source from which micro-organism are isolated may be soil, air, water, compost, milk or food.Isolation of this micro-organism requires specific isolation technique.So a search of micro-organism of our interest in nature can be called as screening.

Screening can be defined as the procedure of isolation, detection and separation of micro-organism from a mixed population of our interest by using highly selective procedure is called Screening”.

The main aim of screening is a selection of valuable and important micro-organism and removal of valueless micro-organism from the microbial population.The procedure used for screening are highly selective and vary from organism to organisms like selective media, selective detection system and selective isolation procedure.In screening isolated colonies are required except in case of  antibiotic-producing micro-organism crowded plate technique is used

In screening of micro-organism, there are three important things that are to be considered

  1. Choice of source- A source from which a sample for screening is taken like air, water, soil, food, milk or compost etc.
  2. Choice of substrate- Required nutrients and growth factors should be supplied for the growth of the desired microorganism.
  3. Choice of Detection- A proper isolation and detection of the desired micro-organism are important.

In the screening of one of the best micro-organism is selected which can give us a maximum yield of product.The best isolation procedure, incubation condition and selection techniques are used.

Here one by one we will go through steps that are important and carried out during Screening

  • Suitable source– The samples that are used for isolation of micro-organism should be collected from a suitable source.The samples collected from a particular source should be diluted.
  • Serial Dilution technique– Serial dilution technique is used to dilute collected samples.Reduction in a number of micro-organism from original sample is called dilution.If the collected sample is solid for example soil then 1 gm of soil is diluted in 10 ml of sterile distilled water.As the sample is solid 10 ml of water is used as the volume should remain same.If the collected sample is in a liquid state, for example, milk or water then 1 ml of milk is diluted in 9 ml of sterile distilled water.This serial dilution is to be applied on suitable agar medium by using a suitable technique like Streaking technique, Spread plate technique, Pour plate technique.These samples are isolated on agar media and further detected.
  • Incubation– Incubation of isolation plates at a suitable temperature for a suitable period of time is very important for getting well-isolated colonies.
  • Detection system– One of the best indicator and detection system used is pH detection system.A suitable agar media with pH indicator system is used for detection of acid or alkaline producing micro-organisms.
  • Purification – Purification of well-isolated colonies is done by re-streaking of the isolated colony on suitable agar media.The dilution which gives 25 to 200 colonies on a plate that dilution is used for getting well-isolated colonies.The efficiency of the medium can be increased by poorly buffering the media.Here in screening, we are detecting the acid or alkaline producing micro-organism and not the amount of acid or alkali produce so we can use the media that is poorly buffered.In case if we want high organic acid producing organism then the media should be strongly buffered.
  • Detection system – In primary detection system, we can only be detected whether acid or alkaline is producing and if acid is produced it may be organic or inorganic acid.Detection of acid is easy but determining the name of acid requires secondary detection system that is the samples are further screened by isolating the samples in liquid media and after incubation, the samples are filtered and thin layer chromatography is carried out to determine the specific acid.


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