The protective effect of L-theanine addition to a cryoprotectant on the storage viability of lactic acid bacteria

Abstract

Abstract There is an increase in the prevalence of mental illness owing to Covid-19 and excessive work stress. Many factors influence mental health. Intestinal health is significantly associated with mental health. Probiotics are beneficial for intestinal health; therefore, research on the correlation between lactic acid bacteria and mental health is ongoing. Lactic acid bacteria (LAB) that metabolize sugars to obtain energy and produce a large amount of lactate through the process, are well known for their benefits. However, they can be used in a large-scale only when good storage stability is guaranteed. The vitality and stability of several LAB strains were effectively protected in this investigation by L-theanine at 1% of the appropriate concentration. (Lactiplantibacillus plantarum MG5023, Enterococcus faecium MG5232, Lactococcus lactis MG4668, Streptococcus thermophilus MG5140, and Bifidobacterium animalis ssp. lactis MG741). The inclusion of L-theanine as a protective agent significantly enhanced the viability of all strains throughout the freeze-drying process compared to that of the non-coated probiotics. The efficacy of L-theanine in improving bacterial stability and survivability was evaluated using accelerated stability tests, gastrointestinal (GI) tract survivability tests and adhesion assays with intestinal epithelial cells. The cell surface was covered with substances including L-theanine, according to morphological findings, providing efficient defense against a variety of external stresses. Therefore, by exerting anti-freezing and anti-thawing properties, the adoption of L-theanine as a new and efficient protective agent may improve the stability and viability of a variety of probiotics.