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Table 1 Overview of methods described in this review.

From: The art of strain improvement of industrial lactic acid bacteria without the use of recombinant DNA technology

Method used Advantages Disadvantages Topic Aim
Random mutagenesis Little knowledge required.
Especially useful for elimination of specific characteristics where direct selection is not possible.
Use of dangerous chemicals.
Mutation bias and hot spots.
Second site mutations will be created.
Requires screening of a large number of survivors.
Pyrimidine auxotrophy Bacteriophage resistance
    Elimination of antibiotic resistance Eliminating unwanted property
    Elimination of citrate metabolism Eliminating unwanted property
    Urease negative mutants of S. thermophilus Eliminating unwanted property
    Lactobacillus strains with low post acidification Improving product stability
Directed evolution Little knowledge required.
Especially useful for complex phenotypes.
Mutagens normally not required.
Multiple mutations may occur.
May require complex experimental setups.
Slow process requiring long time frames.
Selection is at population level, isolated strains must be characterized.
Increasing the growth yield during fermentation Increased efficiency in culture production
Dominant selection Mutagens not required.
Often results in a single mutation.
Requires considerable insight into physiology of the cell.
Analogues may be toxic to humans.
Bacteriophage receptors Bacteriophage resistance
    Conjugation Bacteriophage resistance
    Modifying bacterial cell surfaces Improving texture
    Optimizing the metabolic pathway of EPS Improving texture
    Bacteriophage resistant mutants Improving texture
    Lactobacillus strains with improved ethanol or bile tolerance Improving survival and efficacy
    Lb. helveticus producing succinate Improving flavor
    Altering acidification properties by adapting the carbohydrate metabolism Overcoming effect of a mutation
Recombinant DNA technology Extremely accurate targeted methods. Consumer acceptance. Regulatory approval.
Can be difficult to apply to industrial strains.
Potentially all of the above Potentially all of the above