In recent years, the request for the functional beverages that promote health and wellness has increased. In fact, fermented juices are an excellent delivering means for bioactive components. Their ...production is of crucial importance to supply probiotics, in particular, for people with particulars needs like dairy-product allergic consumers and vegetarians. This review focuses on recent findings regarding the microbial composition and the health benefits of fermented fruit and vegetable beverages by lactic acid bacteria, kefir grains, and SCOBY as well as discussing the metabolites resulting from these fermentations process. Moreover, limits that could restrain their production at the industrial level and solutions that have been proposed to overcome these constraints are also reviewed.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
In this study, the hyperthermophilic dark fermentation of onion wastes (OW) for hydrogen production was investigated. OW were used at different proportions in mixed fruit and vegetable wastes (FVW) ...to evaluate their effect on hydrogen production by
Thermotoga maritima
. Fermentations were performed in a pH-controlled batch stirred tank reactor (BSTR) using seawater as a simplified reaction medium. Results showed that increasing OW proportions in total fruit and vegetable wastes (tFVW) improved H
2
production. Therefore, increasing the OW to tFVW ratio from 0 to 0.8 increased the cumulative H
2
production from 109 to 223.6 mmol/L. The H
2
productivity was also improved from 7.3 to 28.82 mmol/h.L. In fact, OW contain carbohydrates, sulfur compounds, and other nutrients, which were used as a carbon source and energetic substrate for H
2
production by the halophilic bacterium
T. maritima
in seawater without additional chemical compounds. Then, a H
2
yield of 3.36 mol H
2
/mol hexose was achieved using 200 mL of OW, containing 55 mmol/L of carbohydrates. A concept of H
2
production from FVW at high proportions of OW in a simplified reaction medium was proposed. It allowed a H
2
yield of 209 LH
2
/kg volatile solids which could be an interesting future alternative to the current fossil fuel.
Hydrogen (H
2
) is a promising energy carrier owing to its environmentally friendly properties and high energy content. The aim of this work is to achieve a continuous H
2
production from a ...simplified culture medium composed of date wastes (DW) and natural seawater using the marine bacterium,
Thermotoga maritima
. Increasing the dilution rate (
D
) from 0.02 to 0.25 h
− 1
in the continuous stirred tank reactor (CSTR) improved the volumetric H
2
production rate (
Q
H2
) from 2 to 17 mmol/L.h. At a
D
above 0.25 h
− 1
, a washout of the bacterium cells was observed, resulting in a significant decrease of biomass concentration (BC) and then the drop in
Q
H2
. The production of H
2
was improved by using a membrane bioreactor (MBR) due to the cell retention in the reactor. At a high
D
of 0.6 h
− 1
,
the maximum
Q
H2
was increased from 0.6 to 61.75 mmol/L.h, which is higher than those previously reported on continuous H
2
production from different substrates. Moreover, increasing the hexose equivalent concentration in the date juice (DJ) from 30 to 60 mmol/L further enhanced the H
2
production. It allowed a
Q
H2
of 70.2 mmol/L.h which is interesting for a large scale production of H
2
from date wastes.
Graphical Abstract
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This research was carried for the coproduction of two industrial enzymes: α-amylase and protease via SSF by Rhizopus oryzae on humidified bread waste. Fermentation time, inoculum size, initial ...moisture content, salt solutions, and the thickness of the substrate were investigated one by one. Fungus culture was carried out in sterile aluminum trays, and pH was adjusted to 5.5. The main results showed that the highest levels of enzyme production were obtained at 120 h, 65% relative humidity, height media of 1 cm, 105 spore/g, and M-9 solution (g/L): NaH2PO4, 12.8; KH2PO4, 3; NaCl, 0.5; NH4Cl, 1; MgSO4 7H2O, 0.5; CaCl2 2H2O, 0.01. α-Amylase (100 U/g) and protease (2400 U/g) produced by SSF from Rhizopus oryzae (CH4) on BW as substrate are of great interest in industries and could be valorized as enhancers of the bread making process.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Wheat bread is the most popular staple food consumed in Tunisia and, despite the niche production of some typical breads (e.g. Tabouna, Mlawi, Mtabga), the major part is currently produced with ...baker's yeast at industrial or, mainly, at artisanal level, while the use of sourdough fermentation is rarely reported. Considering the growing national demand for cereal baked goods, it can be hypothesized that sourdough fermentation through the use of selected lactic acid bacteria as starters could improve the overall quality and the diversification of local products. Different cereal grains were collected from the regions of Ariana, Bizerta, Beja Nabeul, and Seliana, and the autochthonous lactic acid bacteria were isolated, identified, characterized and selected on the basis of the kinetics of acidification, the proteolytic activity, and the quotient of fermentation. Lactobacillus curvatus MA2, Pediococcus pentosaceus OA2, and Pediococcus acidilactici O1A1 were used together as mixed starter to obtain a selected sourdough. According to the backslopping procedure, a type I sourdough was made from a Tunisian flour (spontaneous sourdough). Compared to the use of the spontaneous sourdough, the one obtained with selected and mixed starters by a unique fermentation step, favored the increase of the concentrations of organic acids, phenols, and total free amino acids, the most suitable quotient of fermentation, and the most intense phytase and antioxidant activities, that increased ca. 20% compared to the control. Moreover, the selected starters improved the in vitro protein digestibility (ca. 82% when selected sourdough was used), textural and sensory features of the breads, as determined by textural profile analysis and panel test, respectively.
This study aimed at exploiting the potential of selected autochthonous lactic acid bacteria and extending the use of a sourdough (type II), thanks to the set-up of a two-step fermentation protocol designed for application at the industrial level, and the confirmed nutritional, textural, and sensory advantages of the final product.
•Lactic acid bacteria were isolated from different Tunisian grains and characterized.•A pool of strains was selected and used for sourdough fermentation.•Selected sourdough was characterized and compared to a spontaneous sourdough.•The advantages of the use of selected starters for bread making were demonstrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•The anaerobic co-digestion of dairy wastewater and cattle manure.•The associated microbial community’s were described by DGGE.•The volatile solids removal and biogas yield reached ...88.6% and 0.87L/g VS.•Syntrophic associations were essential to keep low H2 pressure.•The digestate showed beneficial effects on the plants growth and crops.
The anaerobic co-digestion of dairy wastewater (DW) and cattle manure (CM) was examined and associated with microbial community’s structures using Denaturing Gradient Gel Electrophoresis (DGGE). The highest volatile solids (VS) reduction yield of 88.6% and biogas production of 0.87L/g VS removed were obtained for the C/N ratio of 24.7 at hydraulic retention time (HRT) of 20days. The bacterial DGGE profile showed significant abundance of Uncultured Bacteroidetes, Firmicutes and Synergistetes bacterium. The Syntrophomonas strains were discovered in dependent association to H2-using bacteria such as Methanospirillum sp., Methanosphaera sp. and Methanobacterium formicicum. These syntrophic associations are essential in anaerobic digesters allow them to keep low hydrogen partial pressure. However, high concentrations of VFA produced from dairy wastes acidification allow the growth of Methanosarcina species. The application of the stabilised anaerobic effluent on the agriculture soil showed significant beneficial effects on the forage corn and tomato plants growth and crops.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► The present study aimed at assessing the performance of biofilter packed with peat to treat H2S gas. ► The diversity of the microbial community in the biofilter bed was also evaluated by means of ...SSCP. ► The removal efficiency of H2S reached to 99%, at an EBRT of 60s. ► SSCP profiles demonstrated significant changes in community structure between layers of peat. ► The peat bed may have potential application in H2S biofiltration system.
The objective of this study was to assess the feasibility of using a biofilter system to treat hydrogen sulfide (H2S) contaminated air and to characterize its microbial community. The biofilter system was packed with peat. During the experimental work, the peat was divided in three layers (down, middle, and up). Satisfactory removal efficiencies of H2S were proved and reached 99% for the majority of the run time at an empty bed retention time (EBRT) of 60s. The polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method was used to uncover the changes in the microbial community between the different layers. Analysis of SSCP profiles demonstrated significant differences in community structure from a layer to another with a strong decrease in species diversity towards the up layer. It was found that the used support was suitable for microorganism growth, and may have a potential application in H2S biofiltration system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Strain SulfLac1T, a thermophilic, anaerobic and slightly halophilic, rod-shaped bacterium with a sheath-like outer structure (toga), was isolated from a whey digester in Tunisia. The strain’s ...non-motile cells measured 3–30x1 µm and appeared singly, in pairs or as long chains. The novel strain reduced thiosulfate and elemental sulfur, but not sulfate or sulfite, into sulfide. It grew at 37–65 °C (optimum 55 °C), at pH 6.5–7.9 (optimum pH 6.9) and with 0.2–3 % (w/v) NaCl (optimum 0.5 %). The G+C content of the strain’s genomic DNA was 33.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SulfLac1T was most closely related to Petrotoga mobilis (91.4 % sequence similarity). Based on phenotypic, phylogenetic and chemotaxonomic evidence, strain SulfLac1T represents a novel species of a new genus within the order Thermotogales, for which the name Defluviitoga tunisiensis gen. nov., sp. nov. is proposed. The type strain of the type species is SulfLac1T ( = DSM 23805T = JCM 17210T).
The aim of this study was to isolate lactic acid bacteria from two varieties of grape bunch cultivated in Tunisia (cardinal and red-globe) in order to assess their ability to inhibit the growth of ...their most widespread contaminant,
Aspergillus niger aggrégats
and
Aspergillus carbonarius
. Antifungal activity of 18 isolates was investigated using overlay technique; selected isolates were than identified using 16s rDNA sequence analysis. Isolates with antifungal activities were screened out and studied for their probiotic properties using in vitro tests (tolerance to simulated gastric jus, bile salts, hydrophobicity properties).The most efficient strain was also investigated for its ability to reduce the concentration of ochratoxin A (OTA) on liquid medium. Determination of OTA content in media was released using HPLC analysis. Selected strains (RG7B) (C11C) and (RG8A) showing a good antifungal activities against
Aspergillus niger aggrégats
and
Aspergillus carbonarius
were identified as
Pediococcus pentosaceus
and
Lactobacillus plantarum
, respectively.
Pediococcus pentosaceus
(RG7B) showed promising potential probiotic characteristics and had a high ability for OTA removal after 48 h of incubation in both MRS and PBS media. The OTA removal percentage was significantly higher in MRS than in PBS media (84 and 25%, respectively). This study provides evidence for the control of black
Aspergillus
growth in grape and OTA detoxifying by the use of autochthones LAB strains having antifungal effect and probiotic potential.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Cellulosic fibers from date palm are among the most promising lignocellulose feedstock for biorefinery purposes. The world production is between 1.9 and 2.4 million t/year. Initially, a pretreatment ...with dilute-sulphuric acid of these fibers was performed using a response surface methodology, with temperature and process time as factors. The aim is to produce bioethanol from young and old fibers from date palm, Phoenix dactylifera L. Optimal thermochemical pretreatment conditions for both fibers palms were 220 °C in hydrothermal conditions (without acid); in these conditions pretreated young fibers presented a maximum content in holocelluloses of 45.18% and old fibers 61.97%. Subsequently, during the enzymatic hydrolysis a maximum yield of total reducing sugars (TRS) was reached, 46.32 g/100 g for pretreated dry young fibers and 48.54 g/100 g for pretreated dry old fibers. After enzymatic saccharification, hydrolysates were fermented by Pachysolen tannophilus (ATCC 32691) to ethanol, reaching yields (YE/TRS) of 37.94 g ethanol/100 g of TRS for young fibers and 35.84 g ethanol/100 g of TRS for old fibers. Globally, considering the full process, in the fermentation of the hydrolysates, a yield (YE) of 10.64 g ethanol/100 g of dry young fibers and 10.88 g ethanol/100 g of dry old fibers was reached.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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