Low-cost media from agro-industrial wastes for the cultivation and metabolite production of lactic acid bacteria

Lactic acid bacteria (LAB) are the most well-documented, 'generally regarded as safe' microorganisms used in food fermentation, cosmetics, and pharmaceuticals. Many probiotic strains are utilized for the production of beneficial metabolites, such as bacteriocins and lactic acid, which influence the preservation, organoleptic characteristics, and nutritional properties of food. However, these strains are usually cultured using complex and expensive media, which significantly contribute to the cost of the final product. Thus, this study aims to develop a low-cost alternative medium (LCAM) for the growth and metabolite production of industrially important LAB strains. After several preliminary experiments, an LCAM containing rice bran extract, waste coconut (mature) water, baker's yeast extract, table sugar, and salts was subjected to a statistically-guided optimization study for growth support of a model LAB strain Lactobacillus plantarum BS. Based on the second-order response mathematical model, the optimized medium composition was 35% rice bran extract and 58% waste coconut water, 1% baker's yeast extract, 1% table sugar, and 5% salt solution (LCAM A) plus a modified version without baker's yeast and table sugar (LCAM B). Predicted values were acceptable at 95% (8.91 and 8.88 log CFU/mL) and highly comparable (102% relativity) with the commercial complex medium used as control. Both LCAM formulations were found to support the growth and metabolite production of different LAB genera (L. plantarum BS, Lactococcus lactis NCDO 497, Enterococcus faecalis M4-3, Streptococcus thermophilus BIOTECH 1555, and Pediococcus acidilactici BIOTECH 1068). The LCAM supported the metabolite production of these LAB strains comparable with the commercial medium but is 7.4–7.6-fold cheaper than the cheapest commercial medium. This significant cost reduction has a huge prospect on the large-scale utilization of LAB. Nevertheless, further studies are necessary to enhance the nutritive composition of LCAM for other genera of LAB.