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Although nanometric dead Lactobacillus plantarum has emerged as a potentially important modulator of immune responses, its underlying mechanism of action has not been fully understood. This study aimed to identify the detailed biochemical mechanism of immune modulation by micronized and heat-treated L. plantarum LM1004 (MHT-LM1004, <1 μm in size). MHT-LM1004 was prepared from L. plantarum LM1004 via culture in a specifically designed membrane bioreactor and heat treatment. MHT-LM1004 was shown to effectively induce the secretion of TNF-α and IL-6 and the mRNA expression of inducible nitric oxide synthase (iNOS). MHT-LM1004 enhanced the expression of TLR-2, phosphorylation of MAPKs (ERK), and nuclear translocation of NF-κB in a dose-dependent manner. Oral administration of MHT-LM1004 (4 × 10 9 or 4 × 10 1 1 cells/kg mouse body weight) increased the splenocyte proliferation and serum cytokine levels. These results suggested that MHT-LM1004 effectively enhances early innate immunity by activating macrophages via the TLR-2/MAPK/NF-κB signalling pathway and that this pathway is one of the major routes in immune modulation by the Lactobacillus species.

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Bifidobacterium longum grew at 65 L pilot scale of the membrane bioreactor (MBR), externally fitted with ceramic membrane (0.7 m2). Cell mass at the MBR reached 22.18 g L(-1) as dry cell weight in 12 h, which is 8.44 times higher than cell mass attained at the vial culture. The growth rate in the vial culture was μ = 0.385 h- and at the batch culture was μ = 1.13 h- in the exponential period and μ = 0.31 h(-1) in the stationary period. In the fed-batch mode was μ = 1.102 h(-1) for 6 h with inoculation and declined to μ = 0.456 h(-1) with feeding of feed medium. The growth rate at the MBR was μ = 0.134 h(-1). The number of viable cells was 6.01 × 10(12) cfu L(-1) at the batch culture, but increased to 1.15 × 10(14) cfu L(-1) at the MBR culture. The specific growth rate of viable cell number (colony-forming units per liter, per hour) improved by 6.01 times from the batch to the MBR culture. The wall shear stress mainly generated by the pump, and the membrane incorporated into the MBR was controlled during the cultivation at the MBR. The viability of B. longum declined to under 10% in the first 2 weeks of the 4-week stability test (40° C) as B. longum was exposed to over wall shear stress 713 Pa, but the viability improved to 30-40% in wall shear stress of 260 Pa or STR culture. The loss in the cell viability can be saved by managing with wall shear stress during the cultivation at the MBR.

BACKGROUND: A central problem in the production of lactic acid bacteria (LAB) is the low productivity conventional batch systems due to end product inhibition. This work investigated the impacts of the membrane bioreactor (MBR) on the growth of four industrially important LAB and compared the growth in pH controlled STR using Lactobacillus buchneri, L. brevis, Oenococcus oeni, and Bifidobacterium longum.