Selection of lactic acid bacteria for use in vegetable fermentations

The fermentation of brined vegetables traditionally has depended upon growth of naturally occurring lactic acid bacteria to metabolize the vegetable sugars to organic acids which, together with added salt, results in preservation. Starter cultures have been used only to a limited extent commercially. However, recent efforts to improve fermentation vessels and to develop controlled fermentation methods for fermented vegetables has resulted in an increased interest in developing cultures suitable for application in such methods. Rapid and dominant growth, type and extent of acid production, salt tolerance, temperature range, CO₂ production, cell sedimentation, bacteriophage resistance, nutritional value, and ability to survive as concentrated cultures are factors to consider in developing lactic acid bacterial cultures for use in controlled fermentation of vegetables. Recent examples of efforts to improve cultures include development of nonmalate-decarboxylating strains of lactobacilli for use in cucumber fermentation and isolation of a new species of lactobacillus that produces only the L-isomer of lactic acid from the glucose for use in sauerkraut fermentation. Further improvements in starter cultures for fermented vegetables are likely when suitable genetic transfer systems are developed for selective incorporation or deletion of specific traits.