64 research outputs found
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Optimised production and extraction of astaxanthin from the yeast Xanthophyllomyces dendrorhous
Currently, astaxanthin demand is fulfilled by chemical synthesis using petroleum-based feedstocks. As such, alternative pathways of natural astaxanthin production attracts much research interest. This study aimed at optimising bioreactor operation parameters for astaxanthin production and evaluated strategies for its subsequent extraction. The effect of pH and agitation were evident as significant reduction in both biomass and astaxanthin production was observed when the culture pH was not controlled, and low agitation speed was applied. At controlled pH condition and high agitation speed, significant increase in biomass (16.4 g/l) and astaxanthin production (3.6 mg/l) were obtained. Enzymatic yeast cell lysis using two commercial enzymes (Accellerase 1500 and Glucanex) was optimised using central composite design of experiment (DoE). Accellerase 1500 led to mild cell disruption and only 9% (w/w) of astaxanthin extraction. However, glucanex treatment resulted in complete astaxanthin extractability, compared to standard extraction method (DMSO/acetone). When supercritical CO2 was employed as an extraction solvent in accellerace pre-treated Xanthophyllomyces dendrorhous cells, astaxanthin extraction increased 2.5-fold. Overall, the study showed that extraction conditions can be tailored towards targeted pigments present in complex mixtures, such as in microbial cells
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Waste fat biodegradation and biomodification by Yarrowia lipolytica and a bacterial consortium composed of Bacillus spp. and Pseudomonas putida
Fats, oils and greases (FOGs) are a particular environmental threat. Biodegradation of FOGs is a
challenge and in this study the biodegradation of waste cooking fats, namely butter and olive oil, was studied
using a non-conventional yeast, Yarrowia lipolytica strain LFMB 20, and a bioaugmentation product consisting
of Bacillus spp. and Pseudomonas putida CP1 strain. The microorganisms were grown aerobically in shake-flask
experiments in an enriched medium supplemented with ca 0.85% w/v of waste fat. Analysis of the remaining
substrate showed a removal of ca 90% of the fat by the yeast at the end of the incubation, while the bacteria
removed ca 95% of both fats. Growth rate, biomass production and biomass yield per unit of fat consumed
were all higher for the yeast compared to the bacterial consortium. The bacterial consortium exhibited
autolysis and a significant decrease in its DCW value at the late growth phases of both fat substrate cultures.
The main fatty acids (FAs) present in both fats were linoleic (Δ9,12C18:2), oleic (Δ9C18:1), palmitic (C16:0),
palmitoleic (Δ9C16:1) and stearic (C18:0) acid. Both the bacterial consortium and Y. lipolytica preferentially
removed Δ9C18:1 from the medium, while a negative selectivity against C18:0 was reported. Both inocula
produced microbial mass that contained intra-cellular lipid quantities, but the bacterial consortium gave
significantly higher lipid in DCW values compared with the yeast (maximum values up to ca 63% w/w for the
butter and ca 42% w/w for the olive oil while the respective values for both lipids were 22%±2% w/w for Y.
lipolytica). In all cases, intra-cellular lipids in DCW values decreased during the late growth phases, while their
FA composition differed with those of the substrate fat
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Development of surfactant-coated alginate capsules containing Lactobacillus plantarum
A novel concept is proposed in which alginate capsules containing a model probiotic Lactobacillus plantarum strain are coated with different surfactants with the aim to enhance cell survival during passage initially through simulated gastric (SGF) and then intestinal (SIF) fluid. The surfactants investigated included the anionic sodium dodecyl sulphate (SDS) and ammonium lauryl sulphate (ALS), the cationic dimethyldioctadecylammonium chloride (DDAC), benzalkonium chloride (BZK) and hexadecyltrimethylammonium bromide (CTAB), and the zwitterionic lecithin. Coating the alginate capsules with CTAB, BZK, ALS and SDS resulted in worst survival (~ 4-9 log CFU/g decrease) compared to uncoated capsules (~3 log CFU/g decrease), after 1 hour exposure to SGF and two hours in SIF, which was most likely associated with their gradual penetration inside the microcapsules, as shown by confocal microscopy, and their antimicrobial effects. Coating the alginate capsules with DDAC improved cell survival compared to uncoated capsules (~1.2 CFU/g decrease), whereas coating with lecithin improved cell survival considerably, resulting in almost complete recovery of viable cells in SGF and SIF (~ 0.3 log CFU/g decrease). Although the interaction between alginate and lecithin was relatively weak as demonstrated by turbidity and contact angle measurements, it is likely that the protection was associated with the fact that lecithin was able to penetrate into the capsule rapidly, an observation that was supported by the fact that lecithin enhanced the viability of free cells in SGF and SIF. Lecithin has significant potential of being used as a coating material for probiotic containing capsules
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Impact of ultrasonication on African oil bean (Pentaclethra Macrophylla Benth) protein extraction and properties
African oil bean (Pentaclethra Macrophylla Benth) is an underutilised edible oil seed that could rep-resent a sustainable protein source. In this study, the impact of ultrasonication on the extraction efficiency and properties of protein from African oil bean (AOB) seeds was evaluated. The increase in the duration of extraction favoured the extraction of AOB proteins. This was observed by an increase in extraction yield from 24% to 42% (w/w) when the extraction time was increased from 15 min to 60 min. Desirable properties were observed in extracted AOB proteins; the amino acid profile of protein isolates revealed higher ratios of hydrophobic to hydrophilic amino acids compared to those of the defatted seeds, suggesting alterations in their functional properties. This was also supported by the higher proportion of hydrophobic amino acids and high surface hydrophobicity index value (3813) in AOB protein isolates. The foaming capacity of AOB proteins was above 200%, with an average foaming stability of 92%. The results indicate that AOB protein isolates can be considered promising food ingredients and could help stimulate the growth of the food industry in tropical Sub-Saharan regions where AOB seeds thrive
Supercritical fluid extraction of carotenoids from vegetable waste matrices
The aim of this work was to evaluate a previously-developed model on supercritical fluid extraction (SFE) for carotenoid recovery from carrot peels on various carotenoid-rich fruit and vegetable wastes. To this end, 15 matrices, including flesh and peels of sweet potato, tomato, apricot, pumpkin and peach, as well as flesh and wastes of green, yellow and red peppers, were submitted to SFE under optimised conditions (59 °C, 350 bar, 15 g/min CO2, 15.5% (v/v) ethanol as co-solvent, 30 min of extraction time). The obtained extracts were characterised for their total carotenoid content, antioxidant activity and total carotenoid recovery (TCR). TCR values were greater than 90% w/w for most samples, with β-carotene being the most successfully extracted compound (TCRs 88–100% w/w). More polar carotenoids, such as lutein and lycopene, exhibited lower TCRs. A comparison with literature data suggested that carotenoid extraction is partially dependent on the composition of vegetable matrices, specifically on polysaccharide and moisture content. The results indicated that the optimised SFE conditions can be used as a general model for carotenoid extraction from various fruit and vegetable matrices and as a viable method for adding value to these waste streams by generating carotenoid-rich extracts
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Purification and polymerisation of microbial D-lactic acid from DDGS hydrolysates fermentation
A multi-step process was developed for microbial D-lactic acid purification, followed by poly-D-lactic acid (PDLA) synthesis via azeotropic polycondensation process. Several anion exchange resins were screened for their binding capacity using model lactic acid solutions. Amberlite® IRA67 (weak base anion exchange resin) showed the highest lactic acid adsorption, with maximum adsorption capacity, qmax, of 136.11 mg lactic acid / g of resin, and was further selected to purify D-lactic acid from DDGS hydrolysates through a three-step process; (1) treatment with 7% w/v activated carbon, (2) acidification of fermentation broth (Amberlite® IRA120) and (3) adsorption of lactic acid by anion exchange (Amberlite® IRA67). At the end of the purification process, 80.4% (w/w) D-lactic acid was recovered with 91.8% (w/w) purity, indicating the effectiveness of the developed downstream process. Furthermore, a clear yellowish solid polymer with a molecular weight of 3010 Da was obtained, suitable for applications in biomedical and agricultural sectors
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Adhesion mechanisms mediated by probiotics and prebiotics and their potential impact on human health
Adhesion ability to the host is a classical selection criterion for potential probiotic bacteria that could result in a transient colonisation that would help to promote immunomodulatory effects, as well as stimulate gut barrier and metabolic functions. In addition, probiotic bacteria has a potential protective role against enteropathogens through different mechanisms including production of antimicrobial compounds, reduction of pathogenic bacterial adhesion and competition for host cell binding sites. The competitive exclusion by probiotic bacteria not only has a beneficial effect on the gut but also in the urogenital tract and oral cavity. On the other hand, prebiotics may also act as barriers to pathogens and toxins by preventing their adhesion to epithelial receptors.
In vitro studies with different intestinal cell lines has been widely used along the last decades to assess the adherence ability of probiotic bacteria and pathogen antagonism. However, extrapolation of these results to in vivo conditions still remain unclear, leading to the need of optimization of more complex in vitro approaches that includes interaction with the resident microbiota to address the current limitations.
The aim of this mini-review is to provide a comprehensive overview on the potential effect of the adhesive properties of probiotics and prebiotics on the host by focusing on the most recent findings related with adhesion and immunomodulatory and antipathogenic effect on human health
Lipid production by yeasts growing on commercial xylose in submerged cultures with process water being partially replaced by olive mill wastewaters
Six yeast strains belonging to Rhodosporidium toruloides, Lipomyces starkeyi, Rhodotorula glutinis and Cryptococcus curvatus were shake-flask cultured on xylose (initial sugar – S0 =70±10 g/L) under nitrogen-limited conditions. C. curvatus ATCC 20509 and L. starkeyi DSM 70296 were further cultured in media where process waters were partially replaced by the phenol-containing olive-mill wastewaters (OMWs). In flasks with S0≈100 g/L and OMWs added yielding to initial phenolic compounds concentration (PCC0) between 0.0 g/L (blank experiment) and 2.0 g/L, C. curvatus presented maximum total dry cell weight - TDCWmax ≈27 g/L, in all cases. The more the PCC0 increased, the fewer lipids were produced. In OMW-enriched media with PCC0≈1.2 g/L, TDCW=20.9 g/L containing ≈40% w/w of lipids was recorded. In L. starkeyi cultures, when PCC0≈2.0 g/L, TDCW≈25 g/L was synthesized, whereas lipids in TDCW =24-28% w/w, similar to the experiments without OMWs, were recorded. Non-negligible dephenolization and species-dependant decolorization of the wastewater occurred. A batch-bioreactor trial by C. curvatus only with xylose (S0≈110 g/L) was performed, and TDCW=35.1 g/L (lipids in TDCW=41.3% w/w) was produced. Yeast total lipids were composed of oleic and palmitic and to lesser extent linoleic and stearic acids. C. curvatus lipids were mainly composed of non-polar fractions (i.e. triacylglycerols)
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Supercritical carbon dioxide extraction of phenolic compounds from potato (Solanum tuberosum) peels
In the last three decades, greener technologies have been used, aiming at extracting phenolic
compounds from vegetable matrices due to the inherent advantages compared to organic solventbased
methodologies. In this work, supercritical CO2 was investigated for recovering phenolic acids
from potato peels. Following screening runs for assessing the significant extraction parameters, a
Central Composite Design of Experiments was carried out aiming at process optimization, with
methanol concentration (MeOH, %) and CO2 flow rate (qCO2, g/min) as independent variables. Both
parameters were deemed to impart a significant effect on the final response. Although the major
phenolic acid in potato peels is chlorogenic acid (CGA), the main compound extracted was caffeic
acid (CFA), present at a concentration of 0.75 mg/g dry peel in the extracts. The optimum extraction
conditions were 80 �C, 350 bar, MeOH 20%, and flow rate of 18.0 g/min, which enabled a total
phenolic recovery of 37% and a CFA recovery of 82%. The antioxidant activity of the supercritical
fluid extraction (SFE) extracts was also measured, with the highest scavenging capacity reaching
73%. The need for using mixtures of water and organic solvents as co-solvents in SFE to enable
CGA recovery seems necessary, possibly due to its better dissolution in aqueous solutions than in
pure solvents
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Rapeseed meal hydrolysate as substrate for microbial astaxanthin production
Rapeseed meal, a by-product of oil processing industry, was evaluated as a substrate for astaxanthin production
by the yeast Xanthophyllomyces dendrorhous DSMZ 5626. Four commercial enzymes were tested at different
concentrations (1–15%, v/v) for their ability to break down the cellulosic and hemicellulosic compounds
of rapeseed meal into fermentable sugars. Viscozyme® L and cellulase demonstrated the highest glucose recovery
yields (47–52%, w/w for 15% (v/v) of enzyme loading) with 7–11 g/l of net glucose released in the hydrolysates.
Pectinase and Accellerase® hydrolysates supported the best cell growth and astaxanthin production
in batch shake flask cultures, with maximum biomass of 26 g/l and 15 g/l, respectively, and astaxanthin yields
(YP/X) of 258–332 μg per g of biomass. In batch bioreactor trials, pectinase hydrolysates resulted in high biomass
(42 g/l) and astaxanthin production (11 mg/l) aided by the presence of glycerol (originating from the enzyme
formulation) which served as additional energy and carbon source. Finally, simple glass beads disruption lead
into satisfactory astaxanthin extraction (95%, w/w) in acetone. The findings of this study generate knowledge
towards scale-up potential of microbial astaxanthin production using rapeseed meal hydrolysate as fermentation
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