María Inés Torino

Heterofermentative pattern and exopolysaccharide production by Lactobacillus helveticus ATCC 15807 in response to environmental pH

Aims: The objective of this work was to evaluate the fermentation pattern of and the exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 in milk batch cultures under controlled pH (4·5, 5·0 and 6·2).

Antioxidant and antihypertensive properties of liquid and solid state fermented lentils

The effect of liquid (LSF) and solid state fermentation (SSF) of lentils for production of water-soluble fractions with antioxidant and antihypertensive properties was studied. LSF was performed either spontaneously (NF) or by Lactobacillus plantarum (LP) while SSF was performed by Bacillus subtilis (BS). Native lactic flora in NF adapted better than L. plantarum to fermentative broth and BS counts increased 4.0 logCFU/g up to 48 h of SSF. LSF water-soluble fractions had higher (P ≤ 0.05) free amino groups, GABA content, antioxidant and angiotensin I-converting enzyme inhibitory (ACEI) activities than SSF. In addition, GABA and ACEI activity of LSF increased in a time-dependent manner. Proteolysis by BS was limited, with slight changes in free amino groups, while GABA, total phenolic compounds and antioxidant capacity increased throughout fermentation. Higher antihypertensive potential was observed in NF (96 h) characterised by the highest GABA content (10.42 mg/g extract), ACE-inhibitory potency (expressed as IC(50)) of 0.18 mg protein/ml and antioxidant capacity of 0.26 mmol Trolox equivalents/g extract. Therefore, water-soluble fermented lentil extracts obtained by LSF are particularly promising as functional ingredients in preventing hypertension.

Functionality of exopolysaccharides produced by lactic acid bacteria in an in vitro gastric system

Aims:  To evaluate whether slime‐exopolysaccharides (EPS) or capsular‐polysaccharide (CPS) production could protect the polymer‐producing strains Streptococcus thermophilus CRL 1190 and Lactobacillus casei CRL 87 against the harsh conditions of an in vitro gastric system (GS). EPS stability on the GS was studied.

Biopolymers from lactic acid bacteria. Novel applications in foods and beverages

Lactic acid bacteria (LAB) are microorganisms widely used in the fermented food industry worldwide. Certain LAB are able to produce exopolysaccharides (EPS) either attached to the cell wall (capsular EPS) or released to the extracellular environment (EPS). According to their composition, LAB may synthesize heteropolysaccharides or homopolysaccharides. A wide diversity of EPS are produced by LAB concerning their monomer composition, molecular mass, and structure. Although EPS-producing LAB strains have been traditionally applied in the manufacture of dairy products such as fermented milks and yogurts, their use in the elaboration of low-fat cheeses, diverse type of sourdough breads, and certain beverages are some of the novel applications of these polymers. This work aims to collect the most relevant issues of the former reviews concerning the monomer composition, structure, and yields and biosynthetic enzymes of EPS from LAB; to describe the recently characterized EPS and to present the application of both EPS-producing strains and their polymers in the fermented (specifically beverages and cereal-based) food industry.

A ready-to-use antifungal starter culture improves the shelf life of packaged bread.

Fungal spoilage is the main cause of economic loss in the baking industry. In this study, we developed a ready-to-use biopreserver (slurry [SL]) for nonsliced packed bread by using selected antifungal lactic acid bacteria (LAB) and low-cost ingredients that are compatible with the food matrix. Four LAB strains (Lactobacillus brevis CRL 772, L. brevis CRL 796, L. plantarum CRL 778, and L. reuteri CRL 1100) tested in bread preservation were able to inhibit Penicillium sp. growth and lengthen shelf life twofold with respect to breads prepared using only Saccharomyces cerevisiae (2 days shelf life). The best biopreservation effect (5 days shelf life) was obtained with 40% antifungal slurry SL778 containing L. plantarum CRL 778; this was as effective as 0.2% calcium propionate (PCa). The antifungal effect of SL778 was related to the synthesis of acetic and phenyllactic acid as well as lactic acid, which was produced at a high concentration (31.2 mmol/kg) and lowered the pH of the dough, favoring the undissociated fraction of the organic acids. The combination of the starter SL778 with 0.4% PCa extended the shelf life of packaged bread to 24 days, 2.6-fold longer than breads prepared with only 0.4% PCa.

Multifunctional properties of soy milk fermented by Enterococcus faecium strains isolated from raw soy milk.

Lactic acid bacteria (LAB) isolated from soy milk were used to produce a multifunctional fermented food. Seven isolates were screened for their ability to produce peptides and free isoflavones in soy milk. The antihypertensive, antioxidant, and anti-inflammatory properties of the resulting fermented soy milks were evaluated in vitro using biochemical assays. Isolates 1-5 were found to be producers of fermented soy milk with angiotensin I converting enzyme inhibitory activity (ACEI). Isolate 3 was found to be a producer of free isoflavones that increased the antioxidant and anti-inflammatory potential of fermented soy milk. LAB isolates 2-5 were submitted to genetic profiling and a characterization scheme. These isolates were identified as Enterococcus faecium , and none of them contained virulence determinants or resistance to antibiotics. In conclusion, this study shows that the application of E. faecium isolate 3 for multifunctional food production from soy milk could be a promising strategy in the prevention therapy against cardiovascular disease.

Growth and exopolysaccharide production by Lactobacillus helveticus ATCC 15807 in an adenine-supplemented chemically defined medium

Aims:  To analyse the exopolysaccharide (EPS) production by Lactobacillus helveticus ATCC 15807 in a chemically defined medium (CDM) and the effect of nutrients and stress culture conditions on cell growth and EPS formation.

Mixed-acid fermentation and polysaccharide production by Lactobacillus helveticus in milk cultures

Lactobacillus helveticus grown in milk with pH control at 6.2 had a slower growth rate (μ=0.27 h−1) and produced less exopolysaccharide (49 mg l−1) but increased lactic acid production (425 mM) compared to cultures without pH control (μ=0.5 h−1, 380 mg exopolysaccharide l−1, and 210 mM lactate), respectively. Both cultures displayed a mixed-acid fermentation with formation of acetate, which is linked not only to citrate metabolism, but also to alternative pathways from pyruvate.

Microbial applications in the biopreservation of cereal products

Abstract: Microorganisms play a central role in the manufacture of nutritious fermented foods and beverages. They are also of importance in the maintenance of food storage, food safety, and quality. Cereals and cereal-based products are usually spoiled by bacteria and moulds resulting either in unpleasant texture, smell and odour, or in toxic or poisoning products. The food preservation mediated by microorganisms and fermentation technologies has been attributed to the production of metabolites such as organic acids, hydrogen peroxide, alcohols and antibiotics. Antibiosis by bacteriocins offers potential applications in food biopreservation, while the use of enzymes derived from phages (i.e. enzybiotics) remains as a promising option.