Growth of Lactobacillus reuteri NCIMB 30242 during yogurt fermentation and bile salt hydrolysis activity in the product

International audienceAbstractThe synthesis of bile salt hydrolase has been linked to the health benefit of Lactobacillus reuteri toward lowering blood cholesterol. The aim of this study was to examine the growth and bile salt hydrolysis activity (BSHA) of L. reuteri NCIMB 30242 during milk fermentation with a yogurt starter. There was little growth of L. reuteri during a 4-h co-fermentation with a yogurt culture, and an inoculation of 4.5 × 107 CFU.mL−1 was needed to obtain the 108 CFU.mL−1 target in the product. Enrichment of milk with sugars, minerals, or peptone-based ingredients did not improve growth of L. reuteri. Viable counts of L. reuteri above 1.5 × 108 CFU.mL−1 generated texture defects. Free and microencapsulated (ME) cultures were tested for BSHA in the yogurt drinks. L. reuteri cells which grew during the 4-h lactic fermentation had 40% less BSHA than L. reuteri added directly via the commercial culture. The BSHA of free cells was apparently three times higher than in the ME culture. This study adds data showing that the yogurt production process could affect the functionality of probiotic bacteria

Fermentation technologies for the production of exopolysaccharide-synthesizing Lactobacillus rhamnosus concentrated cultures

The exopolysaccharide (EPS)-producing cultures such as Lactobacillus rhamnosus RW-9595M present a challenge for the culture producers because the high viscosity of the fermented growth medium makes it difficult to recover the cells by centrifugation or filtration. This study examined four approaches to reduce viscosity of the medium while producing high cell densities: incubation temperature, extended incubation in the stationary growth phase, production in alginate gel beads and fed-batch fermentation technology. Automated spectrophotometry (AS) was used to study the effects of temperature, pH and lactate level on growth of the strain. In AS assays, there was no significant difference in final maximal biomass production at temperatures ranging between 34\ub0C to 44\ub0C, but lower yields were noted at 46\ub0C. A pH below 6.0 and a lactate concentration higher than 4% almost completely prevented growth. Under batch fermentation conditions, the viscosity of the medium obtained at 37\ub0C was two fold higher than for 44\ub0C. For cultures produced at 37\ub0C, centrifugation at 10000 g during 5 min did not allow complete recovery of cells, in contrast to cultures grown at 44\ub0C. An extended period of incubation (5 hrs) in the stationary growth phase did not reduce the final viscosity of the growth medium. For similar biomass levels, the glucose-based fed-batch fermentation allowed a 40% reduction in viscosity of the fermented medium in comparison to traditional batch cultures. High-density cell populations (3 x 1010 CFU/g) were obtained when L. rhamnosus RW-9595M was grown in alginate beads. However, overall biomass yields in the immobilized cell bioreactor were half of those obtained in free-cell fermentations. Therefore three methods of producing concentrated EPS-producing cultures are proposed

Effect of the production or use of mixtures of bakers' or brewers' yeast extracts on their ability to promote growth of lactobacilli and pediococci1

Three brewers' and three bakers' yeast extracts (YE) were obtained from five commercial suppliers. They were added to microbiological media and their growth-promoting properties were examined using four lactic cultures ( Lactobacillus casei EQ28 and EQ85, Lactobacillus acidophilus EQ57, Pediococcus acidilactici MA18/5-M). Bakers' YE have a higher total nitrogen content than brewers' YE, but there was not always a correlation between the nitrogen content and growth. A systematic preference for bakers' YE over brewers' YE was only encountered with Lb. casei EQ85, but the other lactic cultures had variable reactions to the source of YE. With Lb. casei EQ85 and Pc. acidilactici 17/5M, mixing of the two sources of YE gave progressively higher growth as a function of the content of the better YE. With Lb. acidophilus EQ57 and Lb. casei EQ28, however, there were instances where a mixture of 75% brewers' YE with 25% bakers' YE gave biomass levels higher than those obtained with the pure products. A series of autolyses were conducted with mixtures of brewers' and bakers' yeast, to see if the YE obtained differed from those obtained from autolysis of the individual yeast cultures. Brewers' yeast autolysates had higher turbidity than those of bakers' yeast. The maximum yield was obtained with the co-autolysis of a combination of 60% bakers' yeasts and 40% brewers' yeasts. Growth of Lb. acidophilus EQ57 was best in the autolysate obtained from 100% brewers' yeast, in spite of the higher nitrogen content of YE produced when bakers' yeast was used during co-autolysis

Viability of Bifidobacterium longum in cheddar cheese curd during manufacture and storage: effect of microencapsulation and point of inoculation

International audienceThe goal of this study was to assess the effect of methods of inoculation on the viability of probiotic bacteria during cheddar cheese manufacture as well as their stability during storage. Bifidobacterium longum ATCC 15708 was freeze-dried and microencapsulated by spray-coating. The effect of inoculation of free whole cell or microencapsulated cells at three points during manufacture (milk before renneting, at cheddaring or at salting) on the viable counts in cheese and whey was investigated. Microencapsulation had no effect on viable counts, chemical parameters (lactose, lactic acid, total nitrogen, nitrogen soluble in TCA, moisture) or sensory properties during manufacturing or storage of the fresh cheeses for 14 days. Inoculation of the bifidobacteria in milk before renneting resulted in higher viable counts in comparison to other points of inoculation. Bifidobacteria added at the salting step, which survived pressing, were subsequently more stable during storage than those inoculated in milk. The stability of B. longum 15708 during storage was greater in the pressed cheeses that in the free curds. The results of this study provides technological data for cheese makers on the optimum point of inoculation as well as the benefit of pressing the curds in order to ensure high levels of probiotics in fresh cheddar cheese

Benefits of a ball and chain: simple environmental enrichments improve welfare and reproductive success in farmed American mink (Neovison vison)

Can simple enrichments enhance caged mink welfare? Pilot data from 756 sub-adults spanning three colour-types (strains) identified potentially practical enrichments, and suggested beneficial effects on temperament and fur-chewing. Our main experiment started with 2032 Black mink on three farms: from each of 508 families, one juvenile male-female pair was enriched (E) with two balls and a hanging plastic chain or length of hose, while a second pair was left as a non-enriched (NE) control. At 8 months, more than half the subjects were killed for pelts, and 302 new females were recruited (half enriched: ‘late E’). Several signs of improved welfare or productivity emerged. Access to enrichment increased play in juveniles. E mink were calmer (less aggressive in temperament tests; quieter when handled; less fearful, if male), and less likely to fur-chew, although other stereotypic behaviours were not reduced. On one farm, E females had lower cortisol (inferred from faecal metabolites). E males tended to copulate for longer. E females also weaned more offspring: about 10% more juveniles per E female, primarily caused by reduced rates of barrenness (‘late E’ females also giving birth to bigger litters on one farm), effects that our data cautiously suggest were partly mediated by reduced inactivity and changes in temperament. Pelt quality seemed unaffected, but E animals had cleaner cages. In a subsidiary side-study using 368 mink of a second colour-type (‘Demis’), similar temperament effects emerged, and while E did not reduce fur-chewing or improve reproductive success in this colour-type, E animals were judged to have better pelts. Overall, simple enrichments were thus beneficial. These findings should encourage welfare improvements on fur farms (which house 60-70 million mink p.a.) and in breeding centres where endangered mustelids (e.g. black-footed ferrets) often reproduce poorly. They should also stimulate future research into more effective practical enrichments