Carboxymethyl cellulose and Pluronic F68 protect the dinoflagellate Protoceratium reticulatum against shear-associated damage

Laboratory- and Pilot-Scale Cultivation of Tetraselmis striata to Produce Valuable Metabolic Compounds

Marine microalgae are considered an important feedstock of multiple valuable metabolic compounds of high biotechnological potential. In this work, the marine microalga Tetraselmis striata was cultivated in different scaled photobioreactors (PBRs). Initially, experiments were performed using two different growth substrates (a modified F/2 and the commercial fertilizer Nutri-Leaf (30% TN-10% P-10% K)) to identify the most efficient and low-cost growth medium. These experiments took place in 4 L glass aquariums at the laboratory scale and in a 9 L vertical tubular pilot column. Enhanced biomass productivities (up to 83.2 mg L^-1 d^-1) and improved biomass composition (up to 41.8% d.w. proteins, 18.7% d.w. carbohydrates, 25.7% d.w. lipids and 4.2% d.w. total chlorophylls) were found when the fertilizer was used. Pilot-scale experiments were then performed using Nutri-Leaf as a growth medium in different PBRs: (a) a paddle wheel, open, raceway pond of 40 L, and (b) a disposable polyethylene (plastic) bag of 280 L working volume. Biomass growth and composition were also monitored at the pilot scale, showing that high-quality biomass can be produced, with important lipids (up to 27.6% d.w.), protein (up to 45.3% d.w.), carbohydrate (up to 15.5% d.w.) and pigment contents (up to 4.2% d.w. total chlorophylls), and high percentages of eicosapentaenoic acid (EPA). The research revealed that the strain successfully escalated in larger volumes and the biochemical composition of its biomass presents high commercial interest and could potentially be used as a feed ingredient.

Recent advances on microalgae cultivation for simultaneous biomass production and removal of wastewater pollutants to achieve circular economy

Microalgae are known for containing high value compounds and its significant role in sequestering carbon dioxide. This review mainly focuses on the emerging microalgae cultivation technologies such as nanomaterials technology that can improve light distribution during microalgae cultivation, attached cultivation and co-cultivation approaches that can improve growth and proliferation of algal cells, biomass yield and lipid accumulation in microalgal. This review includes a comprehensive discussion on the use of microbubbles technology to enhance aerated bubble capacity in photobioreactor to improve microalgal growth. This is followed by discussion on the role of microalgae as phycoremediation agent in removal of contaminants from wastewater, leading to better water quality and high productivity of shellfish. The review also includes techno-economic assessment of microalgae biorefinery technology, which is useful for scaling up the microalgal biofuel production system or integrated microalgae-shellfish cultivation system to support circular economy.

Pathogens and predators impacting commercial production of microalgae and cyanobacteria

Production of phytoplankton (microalgae and cyanobacteria) in commercial raceway ponds and other systems is adversely impacted by phytoplankton pathogens, including bacteria, fungi and viruses. In addition, cultures are susceptible to productivity loss, or crash, through grazing by contaminating zooplankton such as protozoa, rotifers and copepods. Productivity loss and product contamination are also caused by otherwise innocuous invading phytoplankton that consume resources in competition with the species being cultured. This review is focused on phytoplankton competitors, pathogens and grazers of significance in commercial culture of microalgae and cyanobacteria. Detection and identification of these biological contaminants are discussed. Operational protocols for minimizing contamination, and methods of managing it, are discussed.

Isolation and Structural Elucidation of New Amphidinol Analogues from Amphidinium carterae Cultivated in a Pilot-Scale Photobioreactor

The demand for valuable products from dinoflagellate biotechnology has increased remarkably in recent years due to their many prospective applications. However, there remain many challenges that need to be addressed in order to make dinoflagellate bioactives a commercial reality. In this article, we describe the technical feasibility of producing and recovering amphidinol analogues (AMs) excreted into a culture broth of Amphidinium carterae ACRN03, successfully cultured in an LED-illuminated pilot-scale (80 L) bubble column photobioreactor operated in fed-batch mode with a pulse feeding strategy. We report on the isolation of new structurally related AMs, amphidinol 24 (1, AM24), amphidinol 25 (2, AM25) and amphidinol 26 (3, AM26), from a singular fraction resulting from the downstream processing. Their planar structures were elucidated by extensive NMR and HRMS analysis, whereas the relative configuration of the C-32→C-47 bis-tetrahydropyran core was confirmed to be antipodal in accord with the recently revised configuration of AM3. The hemolytic activities of the new metabolites and other related derivatives were evaluated, and structure-activity conclusions were established. Their isolation was based on a straightforward and high-performance bioprocess that could be suitable for the commercial development of AMs or other high-value compounds from shear sensitive dinoflagellates.

Improved delivery of PLGA microparticles and microparticle-cell scaffolds in clinical needle gauges using modified viscosity formulations

Polymer microparticles are widely used as acellular drug delivery platforms in regenerative medicine, and have emerging potential as cellular scaffolds for therapeutic cell delivery. In the clinic, PLGA microparticles are typically administered intramuscularly or subcutaneously, with the clinician and clinical application site determining the precise needle gauge used for delivery. Here, we explored the role of needle diameter in microparticle delivery yield, and develop a modified viscosity formulation to improve microparticle delivery across a range of clinically relevant needle diameters. We have identified an optimal biocompatible formulation containing 0.25% pluronic F127 and 0.25% carboxymethyl cellulose, which can increase delivery payload to 520% across needle gauges 21-30G, and note that needle diameter impacts delivery efficacy. We use this formulation to increase the delivery yield of PLGA microparticles, and separately, PLGA-cell scaffolds supporting viable mesenchymal stem cells (MSCs), demonstrating the first in vitro delivery of this cell scaffold system. Together, these results highlight an optimal formulation for the delivery of microparticle and microparticle-cell scaffolds, and illustrate how careful choice of delivery formulation and needle size can dramatically impact delivery payload.

Effects of shear stress on microalgae - A review

Cultivation of microalgae requires consideration of shear stress, which is generated by operations such as mixing, circulation, aeration and pumping that are designed to facilitate mass and heat transfer as well as light distribution in cultures. Excessive shear stress can cause increased cell mortality, decreased growth rate and cell viability, or even cell lysis. This review examines the sources of shear stress in different cultivation systems, shear stress tolerance of different microalgal species and the physiological factors and environmental conditions that may affect shear sensitivity, and potential approaches to mitigate the detrimental effects of shear stress. In general, green algae have the greatest tolerance to shear stress, followed by cyanobacteria, haptophytes, red algae, and diatoms, with dinoflagellates comprising the most shear-sensitive species. The shear-sensitivity of microalgae is determined primarily by cell wall strength, cell morphology and the presence of flagella. Turbulence, eddy size, and viscosity are the most prominent parameters affecting shear stress to microalgal cells during cultivation.

Membrane technology in microalgae cultivation and harvesting: a review

Membrane processes have long been applied in different stages of microalgae cultivation and processing. These processes include microfiltration, ultrafiltration, dialysis, forward osmosis, membrane contactors and membrane spargers. They are implemented in many combinations, both as a standalone and as a coupled system (in membrane biomass retention photobioreactors (BR-MPBRs) or membrane carbonation photobioreactors (C-MPBRs). To provide sufficient background on these applications, an overview of membrane materials and membrane processes of interest in microalgae cultivation and processing is provided in this work first. Afterwards, discussion about specific aspects of membrane applications in microbial cultivation and harvesting is provided, including membrane fouling. Many of the membrane processes were shown to be promising options in microalgae cultivation. Yet, significant process optimizations are still required when they are applied to enable microalgae biomass bulk production to become competitive as a raw material for biofuel production. Recent developments of the coupled systems (BR-MPBR and C-MPBR) bring significant promises to improve the volumetric productivity of a cultivation system and the efficiency of inorganic carbon capture, respectively.

Bioactives from microalgal dinoflagellates

Dinoflagellate microalgae are an important source of marine biotoxins. Bioactives from dinoflagellates are attracting increasing attention because of their impact on the safety of seafood and potential uses in biomedical, toxicological and pharmacological research. Here we review the potential applications of dinoflagellate toxins and the methods for producing them. Only sparing quantities of dinoflagellate toxins are generally available and this hinders bioactivity characterization and evaluation in possible applications. Approaches to production of increased quantities of dinoflagellate bioactives are discussed. Although many dinoflagellates are fragile and grow slowly, controlled culture in bioreactors appears to be generally suitable for producing many of the metabolites of interest.

Shear-induced changes in membrane fluidity during culture of a fragile dinoflagellate microalga

The commonly used shear protective agent Pluronic F68 (PF68) was toxic to the marine dinoflagellate microalga Protoceratium reticulatum, but had a shear-protective effect on it at concentrations of ≤ 0.5 g L(-1) . Supplementation of P. reticulatum cultures with PF68 actually increased the fluidity of the cell membrane; therefore, the shear protective effect of PF68 could not be ascribed to reduced membrane fluidity, an explanation that has been commonly used in relation to its shear protective effect on animal cells. Data are reported on the membrane fluidity of P. reticulatum and its response to the presence of PF68 under sublethal and lethal turbulence regimens. The membrane fluidity was found to depend strongly on the level of lipoperoxides in the cells produced under lethal agitation.