Development of Chemically Defined Media Supporting High-Cell-Density Growth of Lactococci, Enterococci, and Streptococci

Abstract

Lactococcus lactis IL1403 was used as an experimental strain to develop a chemically defined medium for study of the physiology and metabolic pathways of lactococci. An experimental leave-one-out technique was employed to determine the necessity of each of the 57 chemical components used in medium development. A statistical experimental design approach including three fractional factorial designs and a central composite design was used to optimize the fermentation process with 21 variables composed of 19 nutritional factors grouped from the 57 components and two environmental factors (initial pH and temperature). For L. lactis IL1403, the maximum biomass concentrations obtained with the two optimal chemically defined media developed in this study (ZMB1 and ZMB2) were generally 3.5-to 4-fold higher than the maximum biomass concentrations obtained with the previously described best synthetic media (SA) and 50% to 68% higher than the maximum biomass concentrations obtained with M17, a complex medium commonly used for lactococci. The new chemically defined media support high-cell-density growth of numerous strains of L. lactis, Enterococcus faecalis, and Streptococcus thermophilus.

Development of a Chemically Defined Medium for Better Yield and Purification of Enterocin Y31 fromEnterococcus faeciumY31

“…Therefore, the essential amino acids and stimulatory amino acids were included in the SDM (listed in Table 1). A previous study reported the similar results, as Zhang et al found that six amino acids (arginine, histidine, isoleucine, leucine, methionine, and valine) were necessary for the lactococci, enterococci, and streptococci [20]. Pyridoxal and pantothenic acid are essential B vitamins which had an effect on the growth of E. faecium Y31 and Enterocin Y31 production, and the stimulatory B vitamins mainly included niacin and riboflavin.…”

“…The necessity of magnesium and phosphate has previously been reported by other researchers for various LAB species [20,23,24].…”

Experimental design-aided systematic pathway optimization of glucose uptake and deoxyxylulose phosphate pathway for improved amorphadiene production

“…Furthermore, unlike CM whose composition varies with batches and suppliers, CDM is more reliable and scalable, making it a preferred medium for fed-batch high-cell density cultivations . In addition, the complicated interactions among complex components in CM may interfere with the pathway optimization and kinetic study, thus making data more difficult to interpret (Zhang et al 2009a). It is interesting to note that the AD yield (18 mg/L/OD) using the DXP pathway was among some of the highest yields reported to date Zhou et al 2013).…”

Excess of threonine compared with serine promotes threonine aldolase activity in Lactococcus lactis IL1403

“…However, the strain used in the current study, Lc. lactis IL1403, is known to be auxotrophic for BCAAs (Cocaign-Bousquet et al, 1995;Zhang et al, 2009;Aller et al, 2014), and so this pathway might not be functional in IL1403, although the genes associated with the reactions have been characterized (Bolotin et al, 2001). Moreover, neither of the previously mentioned catabolic reactions of threonine (catalysed by TA and TDH) has been characterized in Lc.…”

“…A chemically defined medium (CDM) is indispensable in studying the metabolic pathways and physiology of microorganisms, because unlike in rich media, all components in a CDM are defined (Zhang et al, 2009). Thus, experiments with CDM produce more comprehensible data, as the substrates and bioproducts can be easily quantified by analytical methods.…”