Lactobacilli or Lactic Acid Bacteria (LAB) are found in the gut and on the skin of all living organisms. They are found in every soil and on every leaf surface. Their abundance signals their importance. LAB have been used for decades in agricultural systems to improve soils, control disease and promote plant growth. However, it was only when Professor Higa began researching their roles that we began to grasp their profound significance and exciting promise. Just as lacto-fermented food remains pathogen-free, the lactic acid in the soil appears to help keep disease organisms in check. Other benefits of LAB include:
- LAB is very effective at improving pore space in soil/soil ventilation
- LAB increases the solubility of fertiliser
- LAB can directly promote plant growth or seed germination, as well as alleviating various abiotic stresses.
- LAB will neutralize ammonia gas produced where the immature compost is applied.
- LAB is conditionally anaerobic, so they can also survive with oxygen.
- LAB solubilizes phosphate – Using LAB in phosphate-accumulated soil will increase its capacity to absorb the insoluble form of phosphates and help overcome the saline disorder as a result of decomposition of the phosphates.
- LAB has served as an effective biocontrol agent; recently LAB has been shown to be effective in the control of a wide variety of fungal and bacterial phytopathogens.
- LAB can improve nutrient availability from compost and other organic material.
- The fermentation pathways provide a more efficient means for utilizing organic substances during their decomposition in soil.
The varied means with which LAB can act as a plant growth promoting bacteria (PGPB) is illustrated below in Figure 1. This shows how LAB can be used in biofertilisers, biocontrol agents and biostimulants to aid in producing food. Lamont in 2017 said “The ability of lactic acid bacteria to live in the plant endosphere suggests an intimate relationship, which is responsible to enhance plant production by improving nutrient availability, acting as a biocontrol agent, alleviating biotic and biotic stresses, and directly stimulating plant growth “
LAB in their own right are a powerful PGPB but added to other complementary microbes, such as those found in EM, further enhances their potency. Lactobacillus plantarum, one of the LAB species in EM, is a particularliy voracious cellulose digesting bacteria who work effectively alongside the fermenting fungi and actinomycetes to accelerate the breakdown of plant residues, creating humus and stimulating aerobic microbes.