Alma Cruz-Guerrero

Probiotics and prebiotics--perspectives and challenges.

Owing to their health benefits, probiotics and prebiotics are nowadays widely used in yogurts and fermented milks, which are leader products of functional foods worldwide. The world market for functional foods has grown rapidly in the last three decades, with an estimated size in 2003 of ca US

Kluyveromyces marxianus CDBB-L-278: A wild inulinase hyperproducing strain

33 billion, while the European market estimation exceeded US

Isolation and identification of killer yeasts from Agave sap ( aguamiel) and pulque

2 billion in the same year. However, the production of probiotics and prebiotics at industrial scale faces several challenges, including the search for economical and abundant raw materials for prebiotic production, the low-cost production of probiotics and the improvement of probiotic viability after storage or during the manufacturing process of the functional food. In this review, functional foods based on probiotics and prebiotics are introduced as a key biotechnological field with tremendous potential for innovation. A concise state of the art addressing the fundamentals and challenges for the development of new probiotic- and prebiotic-based foods is presented, the niches for future research being clearly identified and discussed.

Dissolved oxygen threshold for the repression of endo-polygalacturonase production by Kluyveromyces marxianus

Abstract Kluyveromyces marxianus CDBB-L-278 is an inulinase hyperproducing strain. It was able to grow in a medium containing inulin as the unique carbon source in the presence of 2-deoxyglucose. It produced up to 3.3 times the activity of the control strain K. marxianus NCYC-1429 in an inulin medium, and 3.6 times in a medium with glycerol as the sole carbon source. Although the strain CDBB-L-278 was able to produce inulinase in the presence of 2-deoxyglucose, it was demonstrated that it is not a de-repressed strain since enzyme production was reduced when the concentration of glucose or fructose was increased in the medium. Since inulinase was produced in a glycerol medium without an inducer, it can be considered that the enzyme production was partially constitutive in K. marxianus CDBB-L-278 as well as strain NCYC-1429. The inulinase from K. marxianus CDBB-L-278 was characterized. It had a higher affinity for inulin than for sucrose. Temperature and pH profiles were different for both of these two substrates. The enzyme was stable to high temperatures, with a half-life of 180 min at 50°C.

Commercial probiotic bacteria and prebiotic carbohydrates: a fundamental study on prebiotics uptake, antimicrobials production and inhibition of pathogens.

Wild killer yeasts have been identified as inhibitory to strains used as starters in the production of alcoholic beverages such as beer and wine; therefore, killer or killer-resistant strains have been sought for use in alcoholic fermentations. In the current paper a total of 16 strains belonging to six species were isolated. From two samples of Agave sap (aguamiel) the following yeast strains were isolated: Candida lusitaneae (1), Kluyveromyces marxianus var. bulgaricus (2), and Saccharomyces cerevisiae (capensis) (1). Additionally, in seven samples of pulque (the fermented product), the species C. valida (six strains), S. cerevisiae (chevalieri) (4), S. cerevisiae (capensis) (1), and K. marxianus var. lactis (1) were found. The killer strains were C. valida and K. marxianus var. lactis from pulque and K. marxianus var. bulgaricus from aguamiel. One strain of S. cerevisiae (chevalieri) isolated from pulque which did not show killer activity was, on the other hand, resistant to other killer strains and it had a remarkable ethanol tolerance, suggesting that this strain could be used for alcohol production.

Effect of an Exopolysaccharide-Producing Strain of Streptococcus Thermophilus on the Yield and Texture of Mexican Manchego-Type Cheese

Abstract A detailed study was conducted in terms of the influence of dissolved oxygen (DO) and growth temperature related to the endo-polygalacturonase synthesis by the yeast Kluyveromyces marxianus CDBB-L-278. It was found that 3.3 mg of DO/l was the threshold for the repression of enzyme production. Growth temperature had no effect on the synthesis of this enzyme, but had an indirect effect due to changes in oxygen solubility. Growth rate was influenced by temperature; maintaining the dissolved oxygen constant at 3.3 mg of DO/l, the optimum growth temperature was 40°C. Pectin in the culture medium allowed higher endo-polygalacturonase production; even with 3.3 mg of DO/l, pectin de-repressed the enzyme production.

The Benefits of Probiotics on Human Health

BACKGROUND Probiotics and prebiotics are among the most important functional food ingredients worldwide. The proven benefits of such ingredients to human health have encouraged the development of functional foods containing both probiotics and prebiotics. In this work, the production of antimicrobial compounds coupled to the uptake of commercial prebiotics by probiotic bacteria was investigated. RESULTS The probiotic bacteria studied were able to take up commercial prebiotic carbohydrates to the same or higher extent than that observed for lactose (control carbohydrate). The growth of probiotic bacteria was coupled to the production of antimicrobials such as short-chain fatty acids (SCFA), H2 O2 and bacteriocins. A higher production of antimicrobial compounds was recorded with Oligomate 55® compared with Regulact® and Frutafit® (3-5 and 10-115 times higher SCFA and H2 O2 production, respectively). The probiotic bacteria grown with Oligomate 55® also produced bacteriocins and other non-identified antimicrobial compounds. The antimicrobials produced by the probiotic bacteria inhibited up to 50% the growth of model pathogens such as Escherichia coli, Listeria innocua and Micrococcus luteus compared with control cultures. CONCLUSIONS The results here obtained are useful for the adequate selection of probiotic/prebiotics pairs and therefore in the development of efficient functional foods.

SINGLE CELL PROTEIN | Yeasts and Bacteria

An exopolysaccharide-producing strain of Streptococcus thermophilus was evaluated in the production of Mexican manchego-type cheese. This ropy strain improved water and fat retention, and significantly increased cheese yield. Furthermore, the ropy strain cheese retained more moisture than control cheese during ripening, suggesting that exopolysaccharide strongly bound water within the protein matrix of the cheese. Scanning electron microscopy confirmed that exopolysaccharide bound to the protein matrix of the cheese, producing a dense network that helped to increase water and fat retention and leading to a more open structure of the cheese that gave a softer product, as confirmed by instrumental texture profile analysis and sensory evaluation. Comparison of scanning electron microscopy micrographs of the different sections of the cheese showed higher concentration of exopolysaccharide in the centre than in the outer sections, indicating that exopolysaccharide production continued during ripening and that the environment at the centre of the cheese (moisture and/or oxygen concentration) favoured exopolysaccharide production. Instrumental texture profile analysis also demonstrated that the ropy strain cheese was more cohesive and less elastic than the control; in contrast, exopolysaccharide did not affect chewiness. The changes in texture could be correlated to composition: hardness increased as water and fat decreased, while springiness decreased with increasing fat. The interactions of exopolysaccharide with the cheese protein matrix had an affect on the increase in cohesiveness of the ropy strain cheese.

Antihypertensive and antithrombotic activities of a commercial fermented milk product made with Lactobacillus casei Shirota and Streptococcus thermophilus

Nowadays it is well established that there is a strong relation between diet and health. The concept of using probiotic microorganisms to prevent and treat a variety of human diseases has been used for more than 100 years. Recently, there has been an increase in research of probiotics which has led to significant advances in our understanding of those microorganisms. The importance of probiotics is meaningful because have both, an application on industrial product development and a beneficial effect in human health. In this regard, probiotic microorganisms have been widely added to yogurts and other fermented milks, which are leader products of functional foods comprising approximately 65% of the world functional food market. The action mode of probiotic microorganisms is likely to be multifactorial and seems to be specific for each strain. By modifying the intestinal microbiota, probiotics directly or indirectly influence the state of health through providing end-products of anaerobic fermentation such as vitamins, short chain acids and bacteriocins giving protection against enteric microorganisms. Likewise, probiotic has influence on local and systemic immune responses, improve lactose intolerance symptoms, also stimulates toxin elimination and have other beneficial effects that are not mediated by the intestinal microbiota. In this work, the benefits provided to human health by probiotic microorganisms as well as the mechanisms potentially employed are reviewed and discussed.

Role of Lysine ε-Amino Groups of β-Lactoglobulin on Its Activating Effect of Kluyveromyces lactis β-Galactosidase

Yeasts and bacteria have been particularly important for single-cell protein (SCP) production; they represent the most widely used microorganisms for this purpose: the former mainly for human consumption and the latter frequently used for feed production. Substrates for yeast and bacteria biomass growth include food-processing by-products as well as fossil hydrocarbons. Yeasts have been the preferred source for SCP production over bacteria, particularly for human consumption, as they are related to products, such as bread or beer; however, bacteria have higher protein content, higher yields, and faster growth rate, but they are less accepted for human food. The main drawback for the SCP consumption is its high content of nucleic acids and components of cell wall, which limits its uptake in the diet, at least so that the biomass can be processed to isolate the protein.