Harvesting of Microalgae by Flocculation Branyikova, Irena; Prochazkova, Gita; Potocar, Tomas ...
Fermentation (Basel),
11/2018, Letnik:
4, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Due to increasing demands for microalgal biomass and products originating from microalgae, large-scale production systems are necessary. However, current microalgal production technologies are not ...cost-effective and are hindered by various bottlenecks, one of which is the harvesting of microalgal biomass. Cell separation is difficult because of the low sedimentation velocity of microalgae, their colloidal character with repelling negative surface charges, and low biomass concentrations in culture broths; therefore, large volumes need to be processed in order to concentrate the cells. Flocculation is considered to be one of the most suitable methods for harvesting microalgal biomass. This article provides an overview of flocculation methods suitable for microalgal harvesting, their mechanisms, advantages and drawbacks. Special attention is paid to the role of surface charge in the mechanism of flocculation. The novelty of the review lies in the interconnection between the context of technological applications and physico-chemical surface phenomena.
Among the most important factors influencing beer quality is the presence of well-adjusted amounts of higher alcohols and esters. Thus, a heavy body of literature focuses on these substances and on ...the parameters influencing their production by the brewing yeast. Additionally, the complex metabolic pathways involved in their synthesis require special attention. More than a century of data, mainly in genetic and proteomic fields, has built up enough information to describe in detail each step in the pathway for the synthesis of higher alcohols and their esters, but there is still place for more. Higher alcohols are formed either by anabolism or catabolism (Ehrlich pathway) of amino acids. Esters are formed by enzymatic condensation of organic acids and alcohols. The current paper reviews the up-to-date knowledge in the pathways involving the synthesis of higher alcohols and esters by brewing yeasts. Fermentation parameters affecting yeast response during biosynthesis of these aromatic substances are also fully reviewed.
Worldwide, there is growing interest in achieving a meaningful use of natural resources, as epitomized in this work, which demonstrates the use of saline wastewater (WW) from the demineralization of ...cheese whey as the main component of a medium for cultivation of spirulina (
Limnospira maxima
). Based on Zarrouk medium and the fundamental composition of spirulina biomass, a novel cultivation medium for photoautotrophic cultivation of spirulina was developed. The wastewater medium (WWM) consisted of WW supplemented with NaHCO
3
, urea, K
2
HPO
4
, and FeSO
4
. The suitability of WWM was evaluated by comparison of spirulina growth in laboratory scale tubular or gas-lift photobioreactors in WWM and Zarrouk medium (ZM). The maximum biomass productivity of 0.36 g L
−1
day
−1
was achieved in WWM, compared with 0.24 g L
−1
day
−1
in ZM. The cost of WWM was less than 50% of the cost of ZM.
Curcumin nanoemulsions stabilized by whey protein isolate were successfully developed using high-pressure homogenization. The effect of a chitosan layer deposition using the layer-by-layer technique ...on nanoemulsions' stability was evaluated during storage conditions, as well as during gastrointestinal tract passage. Lipids’ hydrolysis and curcumin bioaccessibility was assessed using a dynamic gastrointestinal model (simulating the stomach, duodenum, jejunum and ileum) and the cytotoxicity, cellular antioxidant activity and permeability analyses were carried out using Caco-2 cells. Results showed that both nanosystems were stable during one month of storage and at stomach pH conditions, whereas creaming and phase separation occurred at intestine pH conditions. The addition of a chitosan layer increased curcumin bioaccessibility, whereas cellular antioxidant activity studies revealed that nanoemulsions and multilayer nanoemulsions exhibited 9 and 10 times higher antioxidant capacity at the cellular level, respectively, when compared to free curcumin. Permeability assays showed that the use of a chitosan layer significantly increased the apparent permeability coefficient of curcumin through Caco-2 cells by 1.55-folds.
•Curcumin nanosystems increase curcumin bioaccessibility.•Nanosystems showed higher cellular antioxidant capacity than free curcumin.•Chitosan can enhance curcumin apparent permeability coefficient by 1.55-fold.•Transcellular and paracellular pathways may exist at the same time.
High-gravity brewing (HGB) is a common practise in industrial breweries. The aim of this study was to examine the effect of HGB on analytical and quality parameters of all-malt beer. Parameters were ...evaluated in bottom-fermented (BF) beer and some data were compared with results from top-fermented (TF) beer. In both, BF and TF beer, two brews were produced where a higher original gravity (OG) beer was diluted to the level of a lower OG beer. Increased ester production was the principal reason for changes in the flavour profile. Especially higher levels of acetate esters (ethyl acetate, isoamyl acetate) affected beer aroma, creating fruity and solvent-like odours. Higher alcohol and acetaldehyde contents were not affected by HGB. The use of HGB for BF beer did not affect important quality parameters such as thiobarbituric acid number (TBA) or foam stability. The content of beer ageing markers (carbonyl compounds) was also not affected by the use of the HGB technology. In sensorial evaluation, differences in flavours of BF HGB beer were evaluated in a triangle test. Beer without dilution was preferred by tasters, commenting on better harmony in bitterness and beer body.
•The concentration of esters in beer is higher when HGB technology is used.•No impact on foam stability in all-malt HGB.•No impact on premature beer aging in all-malt HGB.
Objective
Marine actinomycetes from the genus
Salinispora
have an unexploited biotechnological potential. To accurately estimate their application potential however, data on their cultivation, ...including biomass growth kinetics, are needed but only incomplete information is currently available.
Results
This work provides some insight into the effect of temperature, salinity, nitrogen source, glucose concentration and oxygen supply on growth rate, biomass productivity and yield of
Salinispora tropica
CBN-440
T
. The experiments were carried out in unbaffled shake flasks and agitated laboratory-scale bioreactors. The results show that the optimum growth temperature lies within the range 28–30 °C, salinity is close to sea water and the initial glucose concentration is around 10 g/L. Among tested nitrogen sources, yeast extract and soy peptone proved to be the most suitable. The change from unbaffled to baffled flasks increased the volumetric oxygen transfer coefficient (k
L
a) as did the use of agitated bioreactors. The highest specific growth rate (0.0986 h
−1
) and biomass productivity (1.11 g/L/day) were obtained at k
L
a = 28.3 h
−1
. A further increase in k
L
a was achieved by increasing stirrer speed, but this led to a deterioration in kinetic parameters.
Conclusions
Improvement of
S. tropica
biomass growth kinetics of was achieved mainly by identifying the most suitable nitrogen sources and optimizing k
L
a in baffled flasks and agitated bioreactors.
► Ethanol is one of the most commonly used recreational drugs worldwide. ► Beer market is witnessing a significant increase in the consumption of low-alcohol beer. ► Strategies to produce low alcohol ...beers can be of physical and biological origin. ► Production methods, sensorial properties and additional improvements are reviewed.
The increasing interest of consumers in health and alcohol abuse issues motivates breweries to expand the assortment of products with low alcohol content. The goal of producing beers with low alcohol content can be achieved by two main strategies; namely by gentle removal of alcohol from regular beer and by limited ethanol formation during the beer fermentation. Within these two basic strategies, there are a number of techniques that vary in performance, efficiency and usability. This paper presents an overview and comparison of these techniques and provides an evaluation of sensorial properties of low-alcohol and an alcohol-free beer produced as well as suggests possibilities for their additional improvement.
Due to their bioavailability, glycosylated carotenoids may have interesting biological effects. Sioxanthin, as a representative of this type of carotenoid, has been identified in marine actinomycetes ...of the genus
. This study evaluates, for the first time, the effect of cultivation temperature (T) and light intensity (LI) on the total cellular carotenoid content (TC), antioxidant activity (AA) and sioxanthin content (SX) of a crude extract (CE) from
biomass in its vegetative state. Treatment-related differences in TC and SX values were statistically significantly and positively affected by T and LI, while AA was most significantly affected by T. In the
CE, TC correlated well (R
= 0.823) with SX and somewhat less with AA (R
= 0.777). A correlation between AA and SX was found to be less significant (R
= 0.731). The most significant protective effect against oxidative stress was identified in the CE extracted from
biomass grown at the highest T and LI (CE-C), as was demonstrated using LNCaP and KYSE-30 human cell lines. The CE showed no cytotoxicity against LNCaP and KYSE-30 cell lines.
The unicellular green microalga
is a potential source of a wide range of nutritionally important compounds applicable to the food industry. The aim of this study was to assess the effect of
dried ...biomass on the growth and adherence of 10 strains of
,
and
. The immunomodulatory, antioxidant, and cytotoxic effects of
on human peripheral mononuclear cells and simulated intestinal epithelial cell lines Caco-2 and HT-29 were evaluated. Furthermore, the hypocholesterolemic effects of the microalgae on lipid metabolism in rats fed a high-fat diet were analyzed. The addition of
biomass had a positive effect on the growth of nine out of 10 probiotics and promoted the adherence of three bifidobacteria strains to human cell lines. The antioxidant and immunomodulatory properties of
were concentration-dependent. The inflammatory cytokines (TNF-α and IL-6) were significantly increased following
stimulation at the lowest concentration (0.5%
). Eight week supplementation of
to the diet of hypercholesteromic rats significantly decreased the serum concentrations of LDL-C, VLDL, IDL-B, and IDL-C.
is not cytotoxic in intestinal cell models; it promotes adherence of selected bifidobacteria, it affords immunomodulatory and antioxidant effects, and its addition to diets may help decrease atherosclerosis risk factors.
Wort boiling is one of the most energy-intensive steps in beer production because the isomerization of hop alpha-acids (AA) into iso-alpha-acids (IAA) is a time and energy-consuming process. ...Acceleration of this process by hydrodynamic cavitation (HC), created by a Venturi tube cavitation nozzle, at temperatures below the boiling point, has been tested on a pilot scale. The results show that HC accelerated AA isomerization at all temperatures tested (70–90 °C). The highest HC powered isomerization yield was achieved at 90 °C. However, some quality parameters of the wort were not satisfactory (dimethyl sulphide content, hot break) and therefore the process was extended by a final short boil (10 min). This led to a wort comparable to that obtained after the traditional boiling process (100 °C, 90 min) with a simultaneous 33% energy savings.
•Hydrodynamic cavitation (HC) increased the isomerization yield (Y) of hop alpha-acids.•The highest Y was achieved at 90 °C and cavitation number 0.15.•Some quality parameters of wort produced with HC were not sufficient.•Wort boiling (10 min) after HC-assisted wort treatment improved wort quality.•Complete HC-assisted wort treatment resulted in significant (33%) energy saving.
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