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In this study we assessed the rheological and structural properties of differently acidified and renneted milk gels by controlling pH value and renneting extent. Skim milk were exactly renneted to 4 extents (20, 35, 55, and 74%) and then direct acidified to the desired pH (4.8, 5.0, 5.2, 5.5, 5.8, and 6.2), respectively. Rheological properties were assessed by dynamic rheological measurements, structural properties were studied by spontaneous whey separation and confocal laser scanning micrograph, and protein interactions were studied by dissociation test. Results showed that minimally renneted milk samples (20 and 35%) formed weak gels with low storage modulus, and the acidification range within which gels could form was narrow (pH ≤ 5.2). Highly renneted milk samples formed more gels with high storage modulus. The results of this study revealed that acidification determined the structural properties of highly renneted milk gels. As pH increased from 5.0 to 6.2, highly renneted milk gels had lower loss tangent, decreased spontaneous syneresis, and smaller pores. For both the low and high rennetings, divalent calcium bonds contributed less at low pH than at high pH. In conclusion, renneting increased the pH range suitable for gel formation; acidification determined the spontaneous syneresis and microstructure of highly renneted milk gels.

Aims: Superoxide dismutase (SOD) can prevent and cure inflammatory bowel diseases by decreasing the amount of reactive oxygen species. Unfortunately, short half-life of SOD in the gastrointestinal tract limited its application in the intestinal tract. This study aimed to investigate the treatment effects of recombinant SOD Lactobacillus fermentum in a colitis mouse model. Methods and Results: In this study, we expressed the sodA gene in Lact. fermentum I5007 to obtain the SOD recombinant strain. Then, we determined the therapeutic effects of this SOD recombinant strain in a trinitrobenzene sulphonic acid (TNBS)-induced colitis mouse model. We found that SOD activity in the recombinant Lact. fermentum was increased by almost eightfold compared with that in the wild type. Additionally, both the wild type and the recombinant Lact. fermentum increased the numbers of lactobacilli in the colon of mice (P < 0Á05). Colitis mice treated with recombinant Lact. fermentum showed a higher survival rate and lower disease activity index (P < 0Á05). Recombinant Lact. fermentum significantly decreased colonic mucosa histological scoring for infiltration of inflammatory cells, lipid peroxidation, the expression of pro-inflammatory cytokines and myeloperoxidase (P < 0Á05) and inhibited NF-jB activity in colitis mice (P < 0Á05). Conclusions: SOD recombinant Lact. fermentum significantly reduced oxidative stress and inflammation through inhibiting NF-jB activation in the TNBS-induced colitis model. Significance and Impact of the Study: This study provides insights into the anti-inflammatory effects of SOD recombinant Lact. fermentum, indicating the potential therapeutic effects in preventing and curing intestinal bowel diseases.

Lactobacillus reuteri I5007 has well-documented adhesion properties and health benefits. Future industrial use of Lact. reuteri I5007 will require the development of effective fermentation procedures and high bacterial survival following drying. Therefore, this study was conducted to determine the impact of altering fermentation pH and temperature on the fatty acid composition of the bacterial membranes and subsequent survival of Lact. reuteri I5007 following freeze-drying. Initially, a response surface methodology was used to determine the optimal fermentation pH (5·7) and temperature (37°C), with regard to producing the maximum number of Lact. reuteti I5007 cells. However, when subjected to the optimal fermentation pH and temperature (control treatment), the subsequent survival of Lact. reuteri I5007 following freeze-drying was only 12·95%. Growth at a higher temperature (47°C) or at a neutral pH (pH 6·7) significantly increased the survival of Lact. reuteri I5007 following freeze-drying compared with the control. In contrast, an acidic pH (pH 4·7), or cold (27°C) and extremely cold (4°C) temperatures during fermentation significantly reduced Lact. reuteri I5007 survival following freeze-drying. The fatty acid composition of the membranes of Lact. reuteri I5007 was altered by the different fermentation conditions tested. An increase in the ratio of unsaturated fatty acids (UFA) to saturated fatty acids (SFA) in the bacterial membrane was associated with higher survival of Lact. reuteri I5007. In conclusion, it appears that the use of a higher temperature (47°C) or neutral pH (6·7) during fermentation resulted in increased survival of Lact. reuteri I5007 following freeze-drying. Significance and impact of the study: In this study, we found that a higher fermentation temperature or a neutral pH, rather than cold or acidic conditions, leads to increased survival of Lact. reuteri I5007 during subsequent freeze-drying. This finding has important implications for the future industrial production of this probiotic strain.