Manganese accumulation in probiotic Lactobacillus paracasei ATCC 55544 analyzed by synchrotron X-ray fluorescence microscopy and impact of accumulation on the bacterial viability following encapsulation. (September 2021)

• Record Type: Journal Article
• Authors: Poddar, Devastotra; de Jonge, Martin D.; Howard, Daryl L.; Palmer, Jon; Ainscough, Eric W.; Singh, Harjinder; Haverkamp, Richard G.; Jameson, Geoffrey B.
• Is Part Of: Food research international. Volume 147(2021)
• Publication Date: 2021-09
• Subjects: Lactobacillus paracasei -- Synchrotron X-Ray fluorescence microscopy -- Bacterial viability during storage -- Stationary phase cells -- Elemental composition -- Manganese uptake -- ICP-MS; Food -- Analysis -- Periodicals; Food industry and trade -- Periodicals; Food industry and trade -- Canada -- Periodicals; Food Technology -- Periodicals; Food -- Periodicals; Food-Processing Industry -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Industrie et commerce -- Canada -- Périodiques; Aliments -- Recherche -- Périodiques; Food industry and trade; Canada; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.foodres.2021.110528
• Languages: English
• ISSNs: 0963-9969

Abstract

Graphical abstract: Highlights: Levels of Mn, K and P in probiotic Lactobacillus casei ATCC 55544 were determined by Synchrotron XFM. In Mn-rich environments the viability of L. casei embedded in whole milk powder is greatly enhanced. The results are of importance to seeking ways to improve the shelf life of probiotics. Abstract: Lactobacillus spp. are known to accumulate large amounts of inorganic manganese, which protects against oxidative damage by scavenging free radicals. The ability of probiotic L. paracasei ATCC 55544 to maintain viability during long-term ambient storage may be enhanced by this microorganism's ability to accumulate manganese, which may act as a free radical scavenger. To investigate this hypothesis, X-ray fluorescence microscopy (XFM) was employed to determine the changes in the elemental composition of L. paracasei during growth in the MRS medium with or without added manganese. Moreover, manganese uptake by cells as a function of physiological growth state, early log vs. stationary phase was evaluated. The semiquantitative X-ray fluorescence microscopy results revealed that lower levels of manganese accumulation occurred during the early log phase of bacterial growth of L. paracasei cells (0.0064 µg/cm 2 ) compared with the stationary phase cells (0.1355 µg/cm 2 ). L. paracasei cells grown in manganese deficient MRS medium resulted in lower manganese uptake by cells (0.0027 µg/cm 2 ). The L. paracasei cells were further embedded in milk powder matrix using a fluidized-bed drying technique and stored at a water activity ( a w ) of 0.33 at 25 °C for 15 days. The viability counts of L. paracasei cells grown in MRS medium harvested after 18 h growth and embedded in milk powder matrix retained viability of (9.19 ± 0.12 log CFU/g). No viable L. paracasei cells were observed in the case of embedded L. paracasei cells grown in manganese-deficient MRS medium harvested after 18 h growth or in the case of L. paracasei cells harvested after 4 h when grown in MRS medium. The lower level of manganese accumulation was found to be related to the loss of bacterial viability during storage.