Production and characterization of alginate beads for growth of immobilized Desmodesmus subspicatus and its potential to remove potassium, carbon and nitrogen from sugarcane vinasse

Wastewater treatment process using immobilized microalgae

Microalgae biomass products are gaining popularity due to their diverse applications in various sectors. However, the costs associated with media ingredients and cell harvesting pose challenges to the scale-up of microalgae cultivation. This study evaluated the growth and nutrient removal efficiency (RE) of immobilized microalgae Tetradesmus obliquus in sodium alginate beads cultivated in swine manure-based wastewater compared to free cells. The main findings of this research include (i) immobilized cells outperformed free cells, showing approximately 2.3 times higher biomass production, especially at 10% effluent concentration; (ii) enhanced organic carbon removal was observed, with a significant 62% reduction in chemical oxygen demand (383.46-144.84 mg L-1) within 48 h for immobilized cells compared to 6% in free culture; (iii) both immobilized and free cells exhibited efficient removal of total nitrogen and total phosphorus, with high REs exceeding 99% for phosphorus. In addition, microscopic analysis confirmed successful cell dispersion within the alginate beads, ensuring efficient light and substrate transfer. Overall, the results highlight the potential of immobilization techniques and alternative media, such as biodigested swine manure, to enhance microalgal growth and nutrient RE, offering promising prospects for sustainable wastewater treatment processes.

Calcium alginate elastic capsules for microalgal cultivation

Calcium alginate elastic capsules with a core-shell structure are versatile spherical solid beads that can be produced in large quantities using various techniques. This type of capsule is a promising platform for cell culture applications, owing to its mechanical elasticity and transparency. This paper reports the production of calcium alginate capsules with high consistency, and for the first time, demonstrates the feasibility of the capsules for microalgal cultivation. Cell growth analysis reveals that the vibrationally-shaken calcium alginate elastic capsule platform yielded a higher maximum cell number (4.86 × 108 cells per mL) during the cultivation period than the control solution platforms. Aquafeed and food supplements for humans are the targeted applications of this novel platform.

Comparative study between immobilized and suspended Chlorella sp in treatment of pollutant sites in Dhiba port Kingdom of Saudi Arabia

Dhiba port has a strategic location near the Neom project. Various anthropogenic activities contributed to the discharge of metals, metalloids and oil spills in the aquatic system and caused environmental pollution. Microalgae are the best microorganisms in aquatic conditions known to be capable of eliminating contaminants. In this work the Chlorella sp. was isolated from seawater, the metals, metalloids were determine using ICP- OES (Inductively Coupled Plasma-Optical Emission Spectrometer) and hydrocarbons were determine using GC-MS in different five sites in Dhiba port, after and before treated with Chlorella sp, and immobilized Chlorella sp. The growth parameters (optical density and pigment contents) of Chlorella sp and immobilized Chlorella sp. were investigated during 14 days of grown. The results showed that the most contaminated site by metals and metalloids was site no 3, by Sb, As, Be, Se, and Zn with concentrations 0.07546, 0.05709, 0.09326, 0.4618, and 0.00979 mg/L respectively, and site no 1 was the most contamination by organic compounds, so the site no 1 and site no 3 were chosen to test the efficiency of Chlorella sp. and immobilized Chlorella sp. to remove hydrocarbons and both metals and metalloids. Chlorella sp. and immobilized Chlorella sp. had completely removed metals and metalloids that were present in site 3. There were only 6 compounds remained, after treatments with immobilized alga in site 1. Immobilized Chlorella sp. is the most effective than suspended Chlorella sp in reduces the number of organic compounds in contaminated area. It is an economic tool due to simplifying harvesting and then retaining for further processing.

Encapsulation of Human-Bone-Marrow-Derived Mesenchymal Stem Cells in Small Alginate Beads Using One-Step Emulsification by Internal Gelation: In Vitro, and In Vivo Evaluation in Degenerate Intervertebral Disc Model

Cell microencapsulation in gel beads contributes to many biomedical processes and pharmaceutical applications. Small beads (<300 µm) offer distinct advantages, mainly due to improved mass transfer and mechanical strength. Here, we describe, for the first time, the encapsulation of human-bone-marrow-derived mesenchymal stem cells (hBM-MSCs) in small-sized microspheres, using one-step emulsification by internal gelation. Small (127−257 µm) high-mannuronic-alginate microspheres were prepared at high agitation rates (800−1000 rpm), enabling control over the bead size and shape. The average viability of encapsulated hBM-MSCs after 2 weeks was 81 ± 4.3% for the higher agitation rates. hBM-MSC-loaded microspheres seeded within a glycosaminoglycan (GAG) analogue, which was previously proposed as a mechanically equivalent implant for degenerate discs, kept their viability, sphericity, and integrity for at least 6 weeks. A preliminary in vivo study of hBM-MSC-loaded microspheres implanted (via a GAG-analogue hydrogel) in a rat injured intervertebral disc model demonstrated long-lasting viability and biocompatibility for at least 8 weeks post-implantation. The proposed method offers an effective and reproducible way to maintain long-lasting viability in vitro and in vivo. This approach not only utilizes the benefits of a simple, mild, and scalable method, but also allows for the easy control of the bead size and shape by the agitation rate, which, overall, makes it a very attractive platform for regenerative-medicine applications.

Bioprospecting and selection of tolerant strains and productive analyses of microalgae grown in vinasse

In order to contribute to the biotechnology of microalgae cultivated in vinasse, we carried out the bioprospection of tolerant species and synthesized biomolecules of the total biomass (microalgae and bacteria), recovered from cultures. To use vinasse as a culture medium for the microalgae, waste was centrifuged and used in concentrations from 5 to 50%. Daily cell densities, growth rates, and EC50 values were obtained. After defining the best pair of vinasse concentration/microalgae strain, dry biomass, and composition (proteins and carbohydrates) were determined in 96 h cultures, considering the associated community (bacteria and yeast). The microalgae tested were Chlamydomonas sp., Chlorella sorokiniana, Chlorella vulgaris, Desmodesmus spinosus, Haematococcus pluvialis, Monoraphidium sp., Scenedesmus quadricauda, and Tetraselmis gracilis. The results showed that although the microalgal growth rates in vinasse were similar to controls in BG11, the cells in vinasse had higher biovolumes, dry biomass, and total proteins. The species H. pluvialis, S. quadricauda, and T. gracilis showed the best productivity parameters in vinasse, despite lower growth rates than the other species. Using low concentrations of centrifuged vinasse as a culture medium, only 22% of biological contaminants were present, thus most of the processed biomass was mainly composed of microalgae. Thus, Chlamydomonas sp., D. spinosus, S. quadricauda, and H. pluvialis microalgae have attributes such as resistance and biomolecules that make them candidates for further optimization in production systems, combining the environmental benefits of using waste with the production of biomolecules and/or biomass of commercial interest.