Spray-drying of the microalga Dunaliella salina: effects on beta-carotene content and isomer composition

Biotechnologies for bulk production of microalgal biomass: from mass cultivation to dried biomass acquisition

Microalgal biomass represents a sustainable bioresource for various applications, such as food, nutraceuticals, pharmaceuticals, feed, and other bio-based products. For decades, its mass production has attracted widespread attention and interest. The process of microalgal biomass production involves several techniques, mainly cultivation, harvesting, drying, and pollution control. These techniques are often designed and optimized to meet optimal growth conditions for microalgae and to produce high-quality biomass at acceptable cost. Importantly, mass production techniques are important for producing a commercial product in sufficient amounts. However, it should not be overlooked that microalgal biotechnology still faces challenges, in particular the high cost of production, the lack of knowledge about biological contaminants and the challenge of loss of active ingredients during biomass production. These issues involve the research and development of low-cost, standardized, industrial-scale production equipment and the optimization of production processes, as well as the urgent need to increase the research on biological contaminants and microalgal active ingredients. This review systematically examines the global development of microalgal biotechnology for biomass production, with emphasis on the techniques of cultivation, harvesting, drying and control of biological contaminants, and discusses the challenges and strategies to further improve quality and reduce costs. Moreover, the current status of biomass production of some biotechnologically important species has been summarized, and the importance of improving microalgae-related standards for their commercial applications is noted.

The Influence of the Agglomeration Process on Stability of Microencapsulated β-Carotene

Effects of agglomeration of β-carotene microencapsulated by spray drying on its stability were analysed. Mixtures of Arabic gum (GA), maltodextrin (MD), modified starch (OSA), and whey protein (WP) were used as carriers. GA + MD and OSA + MD microcapsules were subjected to agglomeration. All the samples were stored for 60 days with access to daylight. Stability of the emulsions had a significant effect on efficiency of microencapsulation but had no effect on β-carotene retention during sample storage. Among the tested samples, the highest retention of colorant characterized the samples containing GA + MD. The agglomeration process reduced the content of β-carotene in the microcapsules almost by half. However, retention of the colorant during storage of the microcapsules was increased most of all and half-life of β-carotene was significantly prolonged. Changes in L* and a* colour parameters during storage were more limited in the case of agglomerated samples.

Life cycle evaluation of microalgae biofuels production: Effect of cultivation system on energy, carbon emission and cost balance analysis

The rapid depletion of fossil fuels and ever-increasing environmental pollution have forced humankind to look for a renewable energy source. Microalgae, a renewable biomass source, has been proposed as a promising feedstock to generate biofuels due to their fast growth rate with high lipid content. However, literatures have indicated that sustainable production of microalgae biofuels are only viable with a highly optimized production system. In the present study, a cradle-to-gate approach was used to provide expedient insights on the effect of different cultivation systems and biomass productivity toward life cycle energy (LCEA), carbon balance (LCCO₂) and economic (LCC) of microalgae biodiesel production pathways. In addition, a co-production of bioethanol from microalgae residue was proposed in order to improve the economic sustainability of the overall system. The results attained in the present work indicated that traditional microalgae biofuels processing pathways resulted to several shortcomings, such as dehydration and lipid extraction of microalgae biomass required high energy input and contributed nearly 21 to 30% and 39 to 57% of the total energy requirement, respectively. Besides, the microalgae biofuels production system also required a high capital investment, which accounted for 47 to 86% of total production costs that subsequently resulted to poor techno-economic performances. Moreover, current analysis of environmental aspects of microalgae biorefinery had revealed negative CO₂ balance in producing microalgae biofuels.

In Vitro Effectiveness of Microspheres Based on Silk Sericin and Chlorella vulgaris or Arthrospira platensis for Wound Healing Applications

Some natural compounds have recently been widely employed in wound healing applications due to their biological properties. One such compound is sericin, which is produced by Bombix mori, while active polyphenols, polysaccharides and proteins are synthetized by Chlorella vulgaris and Arthrospira platensis microalgae. Our hypothesis was that sericin, as an optimal bioactive polymeric carrier for microencapsulation process, could also improve the regenerative effect of the microalgae. A solvent-free extraction method and spray drying technique were combined to obtain five formulations, based on algal extracts (C. vulgaris and A. platensis, Chl and Art, respectively) or silk sericin (Ser) or their mixtures (Chl-Ser and Art-Ser). The spray drying was a suitable method to produce microspheres with similar dimensions, characterized by collapsed morphology with a rough surface. Art and Art-Ser showed higher antioxidant properties than other formulations. All microspheres resulted in cytocompatibility on fibroblasts until 1.25 mg/mL and promoted cell migration and the complete wound closure; this positive effect was further highlighted after treatment with Art and Art-Ser. To our surprize the combination of sericin to Art did not improve the microalgae extract efficacy, at least in our experimental conditions.

Carotenoids: From Plants to Food Industry

Carotenoids have been studied for their ability to prevent chronic disease due to the free radical theory of aging in chronic disease etiology. β-carotene, lycopene, zeaxanthine and others carotenoids have antioxidant properties, but the antioxidant capability is variable depending on the in vitro system used The physiology, structure and biochemistry is well described. Moreover, sources of carotenoids and health effects along with bioavailability-absorption and metabolism, of carotenoids are well addressed. The effect of carotenoids on biotechnology and the food industry is significantly attributed. Finally, carotenoids as fortified substances in foods and special aspects about carotenenoids as health promoters are well presented along with a glance of carotenoids economics.

Development of slow release formulations of β-carotene employing amphiphilic polymers and their release kinetics study in water and different pH conditions

β-carotene, a potent antioxidant, has been encapsulated and slow release (SR) formulations were prepared using laboratory synthesized poly(ethylene glycols) (PEGs) based functionalized amphiphilic copolymers. Encapsulation efficiency and loading capacity of the developed formulations were determined which ranged from 22.60 to 28.08 % and 2.2 to 2.8 % respectively. The release kinetics of β-carotene from developed formulations in water revealed increased solubility and prolonged stability of β-carotene. The formulations were further subjected to different pH conditions (viz., 1.8, 6.8 and 7.8) corresponding to human gastrointestinal tract to study the effect of pH on the release of β-carotene. The diffusion exponent (n values) ranged from the 0.1540 to 0.2342 for developed formulation. The results showed that developed slow release formulations were unaffected by the highly acidic conditions referring to the gastric environment of human body. However, the release of β-carotene was high at pH 7.8 and slightly higher at pH 6.8.

Microalgae for "Healthy" Foods-Possibilities and Challenges

  Microalgae have the potential to become a novel source of bioactive molecules, especially for those who might wish to enhance the nutritional and functional quality of foods. Spirulina, one of the most popular microalgae, has been described by the World Health Organization as one of the greatest superfoods on earth serving as an example of the potential of microalgae. This review provides background on current and future uses of microalgae in the human diet, lists the most common species of microalgae used to this end, and describes some production methods used in research and industrial production and recovery. The review also discusses some of the difficulties so far encountered such as low productivities and recovery rates, as well as challenges in the production of compounds of interest. Many scientists and engineers in research centers around the globe are currently dedicated to solve these problems as the various capabilities of microalgae have caught the attention of the energy, environmental, and agricultural industries, we propose that the food industry should as well evaluate the potential of microalgae as a novel source of "health promoting" compounds.

Stability of carotenoids in Scenedesmus almeriensis biomass and extracts under various storage conditions

Scenedesmus almeriensis biomass is a source of carotenoids, particularly lutein, and is considered to be promising as an alternative source to marigold. One key question concerning alternative sources of lutein is the loss of carotenoids that takes place between harvesting and processing, which in the case of marigold is frequently up to 50%. The work described here involved a study into the stability of the main carotenoids (lutein, violaxanthin, and beta-carotene), as well as other components, under different storage conditions. The experiments were carried out with biomass in three forms: frozen, freeze-dried, and spray-dried. The stability of extracts of Scenedesmus biomass in acetone and olive oil was also studied. The results show that the most important factor in retaining carotenoids is a low temperature. At -18 degrees C the loss of carotenoids was negligible after the storage period, regardless of the biomass form used (frozen, freeze-dried, or spray-dried). On the other hand, the carotenoid content and fatty acid profile was increasingly affected with increasing temperature. However, the protein content is unaffected by storage conditions.

Determination of carotenoid stereoisomers in commercial dietary supplements by high-performance liquid chromatography

A method for the determination of beta-carotene, lutein, and zeaxanthin including their cis-isomers and alpha-carotene in commercial dietary supplements by HPLC has been developed. The study comprises 11 oral dosage forms, including 9 soft gelatin capsules, 1 dragée, and 1 effervescent tablet formulation. The capsule content was extracted with an acetone-hexane mixture, and the gelatin shell was digested with papain to release carotenoids that had migrated into the coat. Sample preparation for tablets and dragées was carried out as described for the capsule content. Extraction recoveries exemplified for all-trans-beta-carotene and all-trans-lutein were 95 +/- 5% and 93 +/- 2%, and 95 +/- 2% and 79 +/- 5% after enzymatic treatment, respectively. Apart from all-trans-beta-carotene, its 9-cis- and 13-cis-isomers were detected in all samples, whereas no evidence for cis-isomerization of lutein and zeaxanthin could be obtained. Migration of carotenoids into the shells was only observed in the case of beta-carotene. With the exception of one preparation, the beta-carotene contents determined exceeded the dosage specified on the label by up to 48%, which results from stability overages necessary to compensate for losses during storage.

Stability of beta-carotene in spray dried preparation of Rhodotorula glutinis mutant 32

AIMS

To obtain beta-carotene-rich dry cell preparation from mutant 32 of Rhodotorula glutinis and determination of its pigment stability.

METHODS AND RESULTS

The mutant 32 of R. glutinis was grown in a 14 l stirred tank fermenter. Cell mass was concentrated 10-fold by cross-flow microfiltration and then spray dried. Butylated hydroxy toluene (BHT) and d-tocopherol were used as protecting agents. A two-level, three-variable, factorial optimization was performed to achieve moisture-free, non-viable and beta-carotene-rich feed additive.

CONCLUSIONS

The beta-carotene and cell mass in stirred tank fermenter were found to be 54 +/- 5 mg l-1 and 12.8 +/- 2 g l-1, respectively. In the presence of BHT, 97 +/- 3% (w/w) beta-carotene was recovered for all the inlet temperatures studied. The best beta-carotene and yeast powder recoveries were obtained at 160 degrees C, 11.6% (w/v) cell mass concentration and 1 g l-1 BHT. The pigments inside dried yeast powder were stable in dark and cold condition for at least 10 weeks. The purified beta-carotene got almost totally denatured, under similar conditions of storage, within 76 h.

SIGNIFICANCE AND IMPACT OF THE STUDY

Spray dried and stable preparation of beta-carotene-rich yeast, R. glutinis can provide alternative source of beta-carotene for use in animal nutrition.