Showing papers by "Milena Sinigaglia published in 2019"

Isolation, Screening, and Characterization of Plant-Growth-Promoting Bacteria from Durum Wheat Rhizosphere to Improve N and P Nutrient Use Efficiency

Abstract: The main goal of this paper was to select promising microorganisms which could potentially act as plant-growth-promoting bacteria (PGPB) for durum wheat of Foggia County. At this scope, a new statistical framework, based on multivariate analyses and the evaluation of the statistical distribution of each trait, was used. Four hundred and seventy-four isolates were isolated from the rhizosphere of durum wheat in Foggia County and preliminarily screened as a function of four target indices (ammonium production, siderophores production, P-solubilization, and nitrification). After this step, the number of strains was reduced and the remaining isolates were tested through a quantitative approach, to assess the production of IAA (indole acetic acid), P-mineralization, and nitrification. In this second step, the cut-off was based on the whole population trend by evaluating for each trait the medians and quartiles. As a result, 16 promising isolates were selected and identified by 16S rDNA sequencing (Bacillus, Pseudomonas, Stenotrophomonas, and Lysinibacillus). The last step of this research was a preliminary validation in a growth chamber on eight strains. As screening and simple indices, two quantitative measures were chosen. The main result was the selection of at least three isolates (6P, 20P, and 25A) for a future field validation. They increased biomass and height by respectively 50% and 25%.

Alginate-microencapsulation of Lactobacillus casei and Bifidobacterium bifidum: Performances of encapsulated microorganisms and bead-validation in lamb rennet

Abstract: Lactobacillus casei Lc01 and Bifidobacterium bifidum Bb02 were loaded in 2%-alginate beads and stored at 4 °C for 1 month. After the storage, some technological and probiotic properties were measured on the cells released from beads. Free cells (microorganisms grown at 30–37 °C for 24 h and immediately used) and cells frozen with a cryoprotective agent (33% glycerol) and stored for 1 month were used as negative and positive controls, respectively. The loading of probiotics in beads did not affect acidification (ΔpH of 1.4–1.6), neither growth index at 15 (15–25%), 45 °C (34–45% for Bb02 and 57–67% for Lc01), at pH 9 (46–57%) or in presence of 3% NaCl (75–88%). Concerning the viability at pH 2.5 and in presence of bile salts, the cells released from beads behaved like free ones (viability loss of 2–3 log cfu/mL for both the strains), while frozen cells experienced a stronger cell decrease (5–6 log cfu/mL). As an additional goal, a validation of beads in a lamb rennet was proposed to design a new kind of rennet with “probiotics in” but protected from the harsh conditions. The strains were released from beads and survived for at least 47–49 days.

A Preliminary Report on the Use of the Design of Experiments for the Production of a Synbiotic Yogurt Supplemented With Gluten FriendlyTM Flour and Bifidobacterium infantis.

Abstract: The main goal of this paper was to design a synbiotic yogurt containing Bifidobacterium infantis and Gluten Friendly FlourTM; the proposed approach relies upon milk fermentation through the classical starter of yogurt (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus) to avoid a strong production of acetic acid by bifidobacterial and inoculum of B. infantis after the fermentation. The research was divided in 3 steps. The aim of the first step was the optimization of fermentation kinetic by L. delbureckii and S. thermophilus, by combining the amount of flour (either Gluten Friendly Flour-GF- or Control Flour-CF) in milk, temperature and inoculum level; the factors were combined through a mixture design. As a result of this step, the best combination was pointed out: flour at 2.5 g/l; L. delbrueckii subsp. bulgaricus at 6 log cfu/ml; temperature at 37-40°C. The goal of the second step was to study the effect of flour (2.5 g/l) on the viability of B. infantis. GF prolonged the viability of the probiotic for 14 days. In the last step, a synbiotic yogurt, supplemented with GF and fermented with L. delbureckii and S. thermophilus, and then inoculated with B. infantis, was produced. The product was stored at 8 and 15°C. A positive effect of GF was found at 15°C, with B. infantis at 7.0 log cfu/g in GF sample and 5.5.5.7 log cfu/g in CF sample.

Preliminary Characterization of Yeasts from Bombino Bianco, a Grape Variety of Apulian Region, and Selection of an Isolate as a Potential Starter

Abstract: Eighty-seven yeasts were isolated from Bombino bianco, a white grape variety from Apulian Region (Southern Italy). The isolates were characterized for the splitting of arbutin, the hydrolysis of pectins, sulphite production, the resistance to acetic acid, SO2, and ethanol. An enhanced arbutin splitting (β-glucosidase) and a moderate pectolytic activity were found. Concerning ethanol resistance, the most of yeast population showed a low-to-moderate resistance, but some isolates, identified as Saccharomyces cerevisiae, were able to grow in presence of 15% v/v of ethanol. Four isolates were selected (coded as 43D, 44D, 45D, and 46D), studied for their ability to decarboxylate amino acids and used in small-scale fermentation trial; for this last experiment a reference strain was used (S. cerevisiae EC1118). This experiment suggested the existence of an isolate (S. cerevisiae 46D) with interesting traits and performances, which could be potentially proposed as a starter for Bombino bianco.

Immobilization of Saccharomyces cerevisiae on Apple Pieces to Produce Cider

Abstract: Three yeasts (Saccharomyces cerevisiae var. boulardii, a commercial probiotic yeast; S. cerevisiae W13, a wild yeast able to remove ochratoxin A; and S. cerevisiae 17, a wild yeast with promising probiotic traits) were screened for their ability to adhere on apple pieces as a function of different contact times (15–30 min). Then, apple pieces were stored at 4 °C for 15 days, and the viable count of yeasts was periodically assessed. Yeasts were able to adhere on apple pieces after 15 min (7 log cfu/g) and retained their viability throughout the refrigerated storage. In a second step, apple pieces with S. cerevisiae W13 were used to produce cider on a small scale. The variables under investigation were (a) the recycling of pieces up to 10 times and (b) the preliminary storage of pieces at 4 °C before use. Pieces used immediately after yeast immobilization could be successfully used again 10 times and gained a fermentation performance (in terms of yeast amount in cider and ethanol after 24 h) similar to that achieved by free cells. In addition, the preliminary storage of pieces at 4 °C did not affect their performances as reusable starter carriers.