Acidification Properties Research Articles

Study on the Effect of Inoculation of Mixed Inoculation on Hydrolysis and Acidification Performance of Kitchen Waste

The effect of a mixture of different inoculants as inoculum on the hydrolytic and acidification process was investigated in order to improve the hydrolytic and acidification properties of kitchen waste. The results showed that the inoculation of Baijiu pit mud had the feasibility to improve the hydrolytic acidification performance during the hydrolytic acidification process of kitchen waste. At the end of the hydrolytic acidification process, the SCOD of the 1:0, 3:1,1:1, and 1;3 group increased by 55.97%, 48.67%, 30.82% and 7.03%, respectively, compared with that of the 1:0 group; the hydrolysis rate increased by 2.44%, 7.07%, 2.01% and 2.2% compared with that of the 0:1 group. The highest concentration of VFAs was found in the group with 1:3 ratio of Baijiu pit mud and anaerobic sludge, which was 11353.46 mg/L. The highest acidification rate was found in the 1:3 group, which was 68.57%, and 16.14% higher than that in the 1:0 group. The highest concentration of VFAs was found in the group with 1:3 ratio of Baijiu pit mud and anaerobic sludge, which was 11353.46 mg/L. The highest acidification rate was found in the 1:3 group, which was 68.57%, and 16.14% higher than that in the 1:0 group. Inoculation of Baijiu pit mud was able to change the fraction of VFAs during the hydrolytic acidification of kitchen waste. The fermentation type of the hydrolytic acidification system was ethanol-type fermentation, and the ethanol concentration was increased by 8.64, 8.59, 7.36, and 2.81 times in the groups with the ratio of Baijiu pit mud to anaerobic sludge of 1:0, 3:1, and 1:1, respectively. However, in the Baijiu pit mud and anaerobic sludge ratio of 1:3 and 0:1 group, the main type of fermentation was acetic acid type fermentation. The experimental groups inoculated with Baijiu pit mud.

Degradation Potential of Xerophilic and Xerotolerant Fungi Contaminating Historic Canvas Paintings.

Fungi are important contaminants of historic canvas paintings worldwide. They can grow on both sides of the canvas and decompose various components of the paintings. They excrete pigments and acids that change the visual appearance of the paintings and weaken their structure, leading to flaking and cracking. With the aim of recognizing the most dangerous fungal species to the integrity and stability of paintings, we studied 55 recently isolated and identified strains from historic paintings or depositories, including 46 species from 16 genera. The fungi were categorized as xero/halotolerant or xero/halophilic based on their preference for solutes (glycerol or NaCl) that lower the water activity (aw) of the medium. Accordingly, the aw value of all further test media had to be adjusted to allow the growth of xero/halophilic species. The isolates were tested for growth at 15, 24 °C and 37 °C. The biodeterioration potential of the fungi was evaluated by screening their acidification properties, their ability to excrete pigments and their enzymatic activities, which were selected based on the available nutrients in paintings on canvas. A DNase test was performed to determine whether the selected fungi could utilize DNA of dead microbial cells that may be covering surfaces of the painting. The sequestration of Fe, which is made available through the production of siderophores, was also tested. The ability to degrade aromatic and aliphatic substrates was investigated to consider the potential degradation of synthetic restoration materials. Xerotolerant and moderately xerophilic species showed a broader spectrum of enzymatic activities than obligate xerophilic species: urease, β-glucosidase, and esterase predominated, while obligate xerophiles mostly exhibited β-glucosidase, DNase, and urease activity. Xerotolerant and moderately xerophilic species with the highest degradation potential belong to the genus Penicillium, while Aspergillus penicillioides and A. salinicola represent obligately xerophilic species with the most diverse degradation potential in low aw environments.

Changing Hydrographic, Biogeochemical, and Acidification Properties in the Gulf of Maine as Measured by the Gulf of Maine North Atlantic Time Series, GNATS, Between 1998 and 2018

The Gulf of Maine North Atlantic Time Series (GNATS) has been run since 1998, across the Gulf of Maine (GoM), between Maine and Nova Scotia. GNATS goals are to provide ocean color satellite validation and to examine change in this coastal ecosystem. We have sampled hydrographical, biological, chemical, biogeochemical, and bio‐optical variables. After 2008, warm water intrusions (likely North Atlantic Slope Water [NASW]) were observed in the eastern GoM at 50–180 m depths. Shallow waters (<50 m) significantly warmed in winter, summer, and fall but cooled during spring. Surface salinity and density of the GoM also significantly increased over the 20 years. Phytoplankton standing stock and primary production showed highly‐significant decreases during the period. Concentrations of phosphate increased, silicate decreased, residual nitrate [N*; nitrate‐silicate] increased, and the ratio of dissolved inorganic nitrogen:phosphate decreased, suggesting increasing nitrogen limitation. Dissolved organic carbon (DOC) and its optical indices generally increased over two decades, suggesting changes to the DOC cycle. Surface seawater carbonate chemistry showed winter periods where the aragonite saturation (Ωar) dropped below 1.6 gulf‐wide due to upward winter mixing of cool, corrosive water. However, associated with increased average GoM temperatures, Ωar has significantly increased. These results reinforce the hypothesis that the observed decrease in surface GoM primary production resulted from a switch from Labrador Sea Water to NASW entering the GoM. A multifactor analysis shows that decreasing GoM primary production is most significantly correlated to decreases in chlorophyll and particulate organic carbon plus increases in N* and temperature.

Technological characterization and flavor-producing potential of lactic acid bacteria isolated from traditional dry fermented sausages in northeast China

Thirty-seven lactic acid bacteria (LAB) strains were isolated from traditional dry sausages collected from Northeast China, including Latilactobacillus sakei (29 strains), Lactiplantibacillus plantarum (4 strains), Latilactobacillus curvatus (2 strains), Weissella hellenica (1 strain), and Lactococcus lactis (1 strain). Some LAB strains had tolerance to high concentrations of sodium chloride (6%), sodium nitrite (150 mg/L NaNO2), and acid (pH 4.0). They showed good growth and acidification properties and antimicrobial activity. Among them, five LAB strains that exhibited the best technological properties were selected and inoculated in the sausage model to explore their roles in flavor development. The contents of total free amino acids (FAAs) decreased ranging from 109.11 mg/g to 58.06 mg/g. A total of 46 volatile compounds were identified and the contents of volatile compounds increased in the sausage model during fermentation. Partial least squares regression analysis showed that Lb. sakei HRB10, Lb. plantarum MDJ2, W. hellenica HRB6, and Lc. lactis HRB0 promoted the generation of FAAs and volatile compounds in the sausage model. These findings demonstrated that the autochthonous LAB species are promising for the production of sausage with better flavor and fermentation performance.

In situ exopolysaccharides produced by Lactobacillus helveticus MB2-1 and its effect on gel properties of Sayram ketteki yoghurt

In order to study the mechanism of high viscosity of Sayram ketteki yoghurt, the growth, acidification properties, in situ exopolysaccharides (EPS) production of Lactobacillus helveticus MB2-1 in milk medium were investigated. The microstructure of the yoghurt was analyzed. The characteristics of in situ EPS produced by this strain in yoghurt were studied by high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV–vis) analysis. The amount of in situ EPS produced could be up to 689.47 mg/L. The micrographs of Sayram ketteki yoghurt demonstrated that the in situ EPS secreted by ropy L. helveticus MB2-1 were closely connected with proteins, effectively filling the three-dimensional network structure of casein clusters, thereby resulting in high viscosity of yoghurt. Besides, the molecular weight of in situ EPS was 9.34 × 104 Da, and the in situ EPS was determined to be a new heteropolysaccharide, containing fucose, which made it unique. Moreover, the set yoghurts added with in situ EPS were demonstrated fine effects on the texture improvement. These results illustrated that L. helveticus MB2-1 could be set as a good starter and the in situ EPS could be considered as a probiotic stabilizer substitute for fermented dairy products.

Yoghurt Production Potential of Lactic Acid Bacteria Isolated from Leguminous Seeds and Effects of Encapsulated Lactic Acid Bacteria on Bacterial Viability and Physicochemical and Sensory Properties of Yoghurt

This study aims to determine the yoghurt production potential of lactic acid bacteria isolated from legumes seeds (lentils, beans, cowpea, and broad beans) and examine the effects of alginate capsules of selected starter cultures with high yoghurt production potential on the physicochemical properties, sensory properties of yoghurt, and bacterial viability during storage time at 4°C. The exopolysaccharide (EPS), proteolytic activity, and acidification properties of eight different isolates were determined, and sixteen different yoghurt combinations prepared. The samples showed similar physicochemical (pH, titratable acidity, dry matter, and whey separation), bacterial count, and sensory results in comparison with the commercial yoghurt used as a control sample. The acidity and pH of the yoghurt samples were significantly affected by the storage time. Total solids of yoghurt samples generally tend to decrease and syneresis of yoghurt samples also differed for each starter culture combination during the storage time. The total count of lactic acid bacteria during the storage time was higher than 107 CFU/g. The sensory analysis results of bacterial combinations are significantly different ( p &lt; 0.05 ). Results indicated that isolated starter cultures have potential as commercial starters to improve the quality of yoghurt. Selected starter cultures with yoghurt production potential were encapsulated. Lactic acid bacteria with encapsulation efficiency of 86,3 ± 0,2 and 82,26 ± 0,79 were selected for yoghurt production. The physicochemical properties of the yoghurt with free and encapsulated starter culture were significantly different during the storage time. The reduction (∼0,5 log cfu/g) in the numbers of free and encapsulated starter cultures is over during the storage time ( p &lt; 0.05 ). The acceptability of yoghurt containing encapsulated bacteria was lower than the yoghurt containing free bacteria by the panelists. Consequently, it was determined that alginate capsules increased bacterial viability, but the sensory properties of yoghurt were affected adversely. The LAB isolated form legumes can be introduced to the national microbial collection.

Effect of the cream cooling temperature and acidification method on the crystallization and textural properties of butter

In this study, techno-functional properties of butter were evaluated by modifying the crystallization and acidification properties of cream. For this purpose, the cream obtained from raw milk was allowed to physically ripen at 6 and 8 °C for different periods (10 and 15 h), after which butter was manufactured by using different acidification methods via addition of lactic acid permeate and natural butter culture. It was observed that cream cooling/crystallization temperature and time, as well as acidification method, affected the physicochemical and technological properties of butter but had no significant impact on sensory properties. In butter samples, palmitic acid, stearic acid and myristic acid were the predominant saturated fatty acids, whereas oleic acid content was the highest among the unsaturated fatty acids. The textural properties and hardness values of control butter manufactured by conventional method were higher. Consequently, it could be concluded that amount of diacetyl, one of the characteristic components of butter, in the cream ripened at 6 °C, and the addition of butter starter culture was higher and the hardness values of the butter manufactured from the cream matured for 15 h was lower in comparison to other samples.

Autochthonous and commercial cultures with functional properties in goat milk supplemented with licuri fruit

Autochthonous lactic acid bacteria (LAB) from goat milk were selected to produce fermented goat's milk (FGM) with licuri fruit from the biome of Brazil. The performance of commercial cultures (CC), including Lactobacillus acidophilus (LA-5) and Bifidobacterium animalis subsp. lactis (BB-12) cultures, was compared with that of autochthonous cultures (AC). The AC, including cultures of 10 LAB isolates identified as Lactobacillus plantarum and Lactobacillus rhamnosus, were selected for their acidification properties and evaluated against the CC for their techno-functional properties. The AC showed techno-functional properties similar to or better than those of the CC. For FGM production, two culture mixture were used to give FGM1 (from CC) and FGM2 (from AC). FGM2 showed higher populations, greater acidification and proteolytic activity and less degradation of total phenolic contents over time than FGM1. FGM2 obtained higher scores for sensory attributes and consumer preference. Thus, AC are functional cultures that promote greater sensorial acceptance than CC. The use of AC and the licuri fruit for the FGM production offers the additional benefit of being a local food product.

Isolation and characterization of Streptococcus thermophilus possessing prtS gene from raw milk in Japan.

Streptococcus thermophilus is widely used for producing fermented dairy products such as yogurt and cheese. Some S. thermophilus strains possessing the cell-wall protease PrtS show high proteolytic activity and fast acidification properties, which are very useful in industrial starters. However, few S. thermophilus strains possessing the prtS gene have been isolated from the environment. To clarify whether or not S. thermophilus strains possessing the prtS gene are present in Japan, we isolated S. thermophilus from raw milk collected in Japan from 2011 to 2017 and investigated the strains for the presence of prtS by PCR. A total of 172 S. thermophilus strains were isolated, and 59 strains were confirmed to possess prtS. We measured fermentation times of 59 prtS-positive strains in skim milk broth and found that 53 strains showed fast acidification properties, finishing fermentation within 10 hr. However, the remaining 6 prtS-positive strains showed slow acidification properties, and they had several amino acid mutations in PrtS compared with fast acidifying S. thermophilus LMD-9 and 4F44. These results demonstrate that S. thermophilus strains possessing prtS are prevalent in Japan and that some prtS-positive strains could lose their fast acidifying properties through mutations in PrtS.

Comparison of Bayesian and partial least squares regression methods for mid-infrared prediction of cheese-making properties in Montbéliarde cows

Assessing the cheese-making properties (CMP) of milks with a rapid and cost-effective method is of particular interest for the Protected Designation of Origin cheese sector. The aims of this study were to evaluate the potential of mid-infrared (MIR) spectra to estimate coagulation and acidification properties, as well as curd yield (CY) traits of Montbéliarde cow milk. Samples from 250 cows were collected in 216 commercial herds in Franche-Comté with the objectives to maximize the genetic diversity as well as the variation in milk composition. All coagulation and CY traits showed high variability (10 to 43%). Reference analyses performed for soft (SC) and pressed cooked (PCC) cheese technology were matched with MIR spectra. Prediction models were built on 446 informative wavelengths not tainted by the water absorbance, using different approaches such as partial least squares (PLS), uninformative variable elimination PLS, random forest PLS, Bayes A, Bayes B, Bayes C, and Bayes RR. We assessed equation performances for a set of 20 CMP traits (coagulation: 5 for SC and 4 for PCC; acidification: 5 for SC and 3 for PCC; laboratory CY: 3) by comparing prediction accuracies based on cross-validation. Overall, variable selection before PLS did not significantly improve the performances of the PLS regression, the prediction differences between Bayesian methods were negligible, and PLS models always outperformed Bayesian models. This was likely a result of the prior use of informative wavelengths of the MIR spectra. The best accuracies were obtained for curd yields expressed in dry matter (CYDM) or fresh (CYFRESH) and for coagulation traits (curd firmness for PCC and SC) using the PLS regression. Prediction models of other CMP traits were moderately to poorly accurate. Whatever the prediction methodology, the best results were always obtained for CY traits, probably because these traits are closely related to milk composition. The CYDM predictions showed coefficient of determination (R2) values up to 0.92 and 0.87, and RSy,x values of 3 and 4% for PLS and Bayes regressions, respectively. Finally, we divided the data set into calibration (2/3) and validation (1/3) sets and developed prediction models in external validation using PLS regression only. In conclusion, we confirmed, in the validation set, an excellent prediction for CYDM [R2 = 0.91, ratio of performance to deviation (RPD) = 3.39] and a very good prediction for CYFRESH (R2 = 0.84, RPD = 2.49), adequate for analytical purposes. We also obtained good results for both PCC and SC curd firmness traits (R2 ≥ 0.70, RPD ≥1.8), which enable quantitative prediction.

Growth and development of Arabidopsis thaliana seedlings in interaction with fungi isolated from stem-end rot of avocado fruits

The influence of Phomopsis viticola, Diaporthe phaseolorum and Pseudofusicoccum stromaticum isolated from avocado stem-end rot on growth of Arabidopsis seedlings was investigated. We found responses that are specific for each fungus, whereas P. viticola and D. phaseolorum strongly repressed root growth, P. stromaticum induced growth and branching, and enhanced shoot biomass production. Detailed microscopy and structural analyses revealed that the fungi did not affect cell division in root meristems but rather influenced cell elongation and differentiation, and these responses were related to changes in auxin responsiveness. P. stromaticum strongly acidifies the growth medium and this correlated with induction of the jasmonic acid responsive gene construct LOX2:GUS in leaves, whereas P. viticola and D. phaseolorum showed much reduced acidification properties. Taken together, our results show that fungal isolates from the stem-end of avocado fruits interact with Arabidopsis plants in highly diverse and contrasting manners influencing growth, patterning and defence.

High-throughput pH monitoring method for application in dairy fermentations.

Optimization of dairy fermentation processes often requires multiplexed pH measurements over several hours. The method developed here measures up to 90 samples simultaneously, where traditional electrode-based methods require a lot more time for handing the same number of samples. Moreover, the new method employs commonly used materials and can be used with a wider range of fluorescence readers than commercial 96-well plates with optical pH sensors. For this application, a milk-like transparent medium is developed that shows acidification properties with dairy starters that are similar to milk. Combination of this milk-like medium and 3 fluorescent indicators allow precise measurements of pH in a range of 4·0-7·0. The new method showed much higher throughput compared to the benchmark electrode systems while being as accurate, as shown by successful application for a comparison of various dairy starter cultures and for optimizing the inoculation rate.

Use of Carnobacterium spp protective culture in MAP packed Ricotta fresca cheese to control Pseudomonas spp

Ricotta fresca is a whey cheese susceptible of secondary contamination, mainly from Pseudomonas spp. The extension of the shelf life of refrigerated ricotta fresca could be obtained using protective cultures inhibiting the growth of this spoilage microorganism. A commercial biopreservative, Lyofast CNBAL, comprising Carnobacterium spp was tested against Pseudomonas spp. The surface of ricotta fresca samples were inoculated either with Pseudomonas spp or Pseudomonas and Carnobacterium spp. Samples were MAP packed, stored at 4 °C and analyzed the day of the inoculum and 7, 14 and 21 days after the contamination. Microbiological analyses included total bacterial count, mesophilic lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp, Listeria monocytogenes, moulds and yeasts. Pseudomonas mean initial contamination level was comparable in blank and artificially inoculated samples, respectively with values of 2.15 ± 0.21 and 2.34 ± 0.26 log cfu g−1. Carnobacterium spp. significantly reduced the growth of Pseudomonas spp respectively of 1.28 log and 0.83 log after 14 and 21 days of refrigerated storage. Intrinsic properties and physico-chemical composition were also investigated. Limited variation of pH was observed in samples inoculated with the protective cultures, indicating low acidification properties of Carnobacterium spp. Instead, no significant differences were observed for aW, moisture, fat and proteins during storage and between inoculated and control samples.

Evaluation of functionally important lactic acid bacteria and yeasts from Nigerian sorghum as starter cultures for gluten-free sourdough preparation

There is an increasing prevalence of celiac disease, which is gradually encroaching into Africa and Nigeria ranks first among sorghum-producing African countries. It is important to select starter cultures that can improve the functional properties of peculiar flour such as sorghum for the development of novel gluten-free diets. Therefore, this study aimed at screening of functionally important lactic acid bacteria (LAB) and yeasts as starter cultures for the development of sorghum-based sourdough. A total of 103 LAB and 20 yeast isolates obtained from Nigerian sorghum flour were screened for functional properties essential for sourdough preparation. Three LAB isolates were selected based on proteolytic activities, exopolysaccharide production and acidification properties, while one yeast strain was selected based on its gas production ability, low pH and acetic acid tolerance. Pediococcus pentosaceus SA8, Weissella confusa SD8 and P. pentosaceus LD7 showed highest proteolytic activity (24.7 mm), exopolysaccharide production (753.3mg/100 ml) and acidification property (0.25 g/100 g lactic acid) respectively. Saccharomyces cerevisiae YC1 had vigorous gas production (CO2 > 20 mm at 8 h), tolerated pH 2.5 and 0.1% acetic acid, and had highest leavening activities (60.87% at 1 h). The selected LAB and yeast strains possessed promising attributes as functional starter cultures for the production sourdoughs breads.

Sourdough-type propagation of faba bean flour: Dynamics of microbial consortia and biochemical implications

The microbial ecology of faba bean sourdoughs obtained from an Italian (Ita) and a Finnish (Fi) cultivar, belonging respectively to Vicia faba major and V. faba minor groups, was described by 16S rRNA gene pyrosequencing and culture-dependent analysis. The sourdoughs were propagated with traditional backslopping procedure throughout 14days. Higher microbial diversity was found in the sourdough deriving from V. faba minor (Fi), still containing residual hulls after the milling procedure. After 2days of propagation, the microbial profile of Ita sourdough was characterized by the dominance of the genera Pediococcus, Leuconostoc and Weissella, while the genera Lactococcus, Lactobacillus and Escherichia, as well as Enterobacteriaceae were present in Fi sourdoughs. Yeasts were in very low cell density until the second backslopping and were not anymore found after this time by plate count or pyrosequencing analysis. Among the lactic acid bacteria isolates, Pediococcus pentosaceus, Leuconostoc mesenteroides and Weissella koreensis had the highest frequency of occurrence in both the sourdoughs. Lactobacillus sakei was the only lactobacillus isolated from the first to the last propagation day in Fi sourdough. According to microbiological and acidification properties, the maturity of the sourdoughs was reached after 5days. The presence of hulls and the different microbial composition reflected on biochemical characteristics of Fi sourdoughs, including acidification and phenolic compounds. Moreover, proteolysis in Fi sourdough was more intense compared to Ita. The microbial dynamic of the faba bean sourdoughs showed some differences with the most studied cereal sourdoughs.

Impact of Sorghum and Nabag (&amp;lt;i&amp;gt;Ziziphusspina-Christi&amp;lt;/i&amp;gt;) Pulp Fruit Lactic Acid Bacteria Sourdoughs on Fermentation Properties of Dough, Quality and Shelf Life of Wheat Bread

Sourdoughs were produced from sorghum and nabag flour using <i>Lactobacillus plantarum</i> and <i>L. brevis</i> and added to a basic bread formulation (10% and 20% addition levels). Dough fermentation, quality and shelf life of wheat bread were examined. Acidification characteristics (pH and total titratable acidity), total bacteria count, fermentation end-products (malic acid, lactic acid, acetic acid, citric acid, succinic acid, fumaric acid and ethanol) and soluble carbohydrates (arabinose, galactose and glucose) contents were measured during both sorghum sourdough and nabag sourdough. Some differences between <i>L. plantarum</i> and <i>L. brevis</i> in acidification properties, fermentation end-products and soluble carbohydrates availability were observed both in sorghum sourdough and nabag sourdough. Addition of sorghum and nabag sourdough starters progressively decrease pH and increased TTA values compared to the control dough and bread. Addition of sorghum and nabag sourdough significantly decreased dough water absorption and increased maximum gas fermentation height, total gas volume, gas retention volume, thereby sorghum and nabag sourdough has positive effect to improve of the fermentation properties of dough. The results showed that dough prepared with 10% and 20% sorghum and nabag sourdough starters had a positive impact on bread quality properties, whereas nabag sourdough starters showed higher volume and moisture content and better textural properties during storage than samples of sorghum sourdough and control.

Wnt directs the endosomal flux of LDL ‐derived cholesterol and lipid droplet homeostasis

The Wnt pathway, which controls crucial steps of the development and differentiation programs, has been proposed to influence lipid storage and homeostasis. In this paper, using an unbiased strategy based on high-content genome-wide RNAi screens that monitored lipid distribution and amounts, we find that Wnt3a regulates cellular cholesterol. We show that Wnt3a stimulates the production of lipid droplets and that this stimulation strictly depends on endocytosed, LDL-derived cholesterol and on functional early and late endosomes. We also show that Wnt signaling itself controls cholesterol endocytosis and flux along the endosomal pathway, which in turn modulates cellular lipid homeostasis. These results underscore the importance of endosome functions for LD formation and reveal a previously unknown regulatory mechanism of the cellular programs controlling lipid storage and endosome transport under the control of Wnt signaling.

The Use of Lactic Acid Bacteria Starter Culture in the Production of Nunu, a Spontaneously Fermented Milk Product in Ghana.

Nunu, a spontaneously fermented yoghurt-like product, is produced and consumed in parts of West Africa. A total of 373 predominant lactic acid bacteria (LAB) previously isolated and identified from Nunu product were assessed in vitro for their technological properties (acidification, exopolysaccharides production, lipolysis, proteolysis and antimicrobial activities). Following the determination of technological properties, Lactobacillus fermentum 22-16, Lactobacillus plantarum 8-2, Lactobacillus helveticus 22-7, and Leuconostoc mesenteroides 14-11 were used as single and combined starter cultures for Nunu fermentation. Starter culture fermented Nunu samples were assessed for amino acids profile and rate of acidification and were subsequently evaluated for consumer acceptability. For acidification properties, 82%, 59%, 34%, and 20% of strains belonging to Lactobacillus helveticus, L. plantarum, L. fermentum, and Leu. mesenteriodes, respectively, demonstrated fast acidification properties. High proteolytic activity (>100 to 150 μg/mL) was observed for 50% Leu. mesenteroides, 40% L. fermentum, 41% L. helveticus, 27% L. plantarum, and 10% Ent. faecium species. In starter culture fermented Nunu samples, all amino acids determined were detected in Nunu fermented with single starters of L. plantarum and L. helveticus and combined starter of L. fermntum and L. helveticus. Consumer sensory analysis showed varying degrees of acceptability for Nunu fermented with the different starter cultures.

Physico‐Chemical Properties of Sourdough Bread Production Using Selected Lactobacilli Starter Cultures

AbstractThe acidification properties and technological performance (dough elasticity and bread volume) of four individual lactic acid bacteria (LAB) starter cultures (Lactobacillus delbrueckii subsp. bulgaricus LB18; Lactobacillus delbrueckii subsp. bulgaricus CNRZ 737; Lactobacillus delbrueckii subsp. bulgaricus 2483; Lactobacillus helveticus LH30) were investigated in relation to dough and bread quality derived from a sourdough fermentation. A plain dough mixture (without LAB starter cultures) was used as a control against the sourdough systems with added cultures. The exopolysaccharide (EPS) producing LAB starter cultures significantly increased dough stickiness and extendibility compared with the plain dough system. Total EPS production by the LAB cultures during sourdough formation differed depending on the culture used (in the order of NCFB 2483 &gt; Z737 &gt; LB18 &gt; LH30). The viscoelastic nature of the dough was increased with the use of LAB cultures. Bread volume significantly increased with the inclusion of EPS cultures. Bread staling (as determined by the extent of firming of bread) was reduced with the use of ropy cultures. Increased exopolysaccharide production during dough formation appeared to be associated with reduced staling and increased bread volume.Practical ApplicationsSourdough bread and cereal products have experienced increased attention from consumers for either health or sensorial reasons. The current research investigate the potential use of a selected range of exopolysaccharide producing starter strains in an attempt to characterise textural and sensorial qualities derived from ropy and nonropy lactic acid bacteria (LAB) starter cultures. The results indicate a clear potential for these LAB cultures in improving consumer quality and shelf‐life stability of sourdough products.

Mechanisms and Remediation Technologies of Sulfate Removal from Acid Mine Drainage

Acid mine drainage (AMD) has properties of extreme acidification, quantities of sulfate and elevated levels of soluble heavy metals. It was a widespread environmental problem that caused adverse effects to the qualities of ground water and surface water. In the past decades, most of investigations were focused on the heavy metals as their toxicities for human and animals. As another main constitution of AMD, sulfate ion is nontoxic, yet high concentration of sulfate ion can cause many problems such as soil acidification, metal corrosion and health problems. More attention should be paid on the sulfate ion when people focus on the AMD. In the paper, sulfate removal mechanisms include adsorption, precipitation, co-precipitation and biological reduction were analyzed and summarized. Meanwhile, the remediation technologies, especially the applications of them in China were also presented and discussed.