Isolation and optimization of a novel thraustochytrid strain for DHA rich and astaxanthin comprising biomass as aquafeed supplement

Seasonal dynamics of thraustochytrids in mangrove rhizospheres for microbial interactions, PUFA production

This study investigated seasonal variations of thraustochytrids in rhizosphere soil collected from two mangrove species Rhizophora apiculata and Avicennia marina in natural and planted mangrove stands. Thraustochytrid counts were higher in the natural mangrove stand than in the planted site. The counts varied seasonally, being highest in the post-monsoon season followed by summer, monsoon, and pre-monsoon. Thraustochytrid counts exhibited positive correlations (p < 0.01) with counts of Total heterotrophic bacteria (THB), azotobacters, actinobacteria, fungi, yeasts, and Trichoderma. However, a negative correlation was observed with cyanobacteria. The counts also had positive correlation with silt, clay, nitrogen, phosphorus, potassium, chromium, copper, magnesium, cadmium, zinc and redox potential, but, negative correlations with temperature, pH, pore water salinity, total organic carbon and sand content of the soil samples. In the present study, 113 thraustochytrid strains were isolated from mangrove habitats. However, only 48 pure cultures survived after being sub-cultured three times. Based on survivability, color, and shape, two isolates from each sampling site in each season were selected. The predominant 24 isolates were identified based on their morphological, and molecular characteristics and were classified under five genera: Thraustochytrium, Schizochytrium, Botryochytrium, Parietichytrium, and Aurantiochytrium. Among the isolates, Aurantiochytrium sp. (AKTSK-06) produced the highest biomass of 15.71 g/L in the post-monsoon season (January-March, 2023), and Aurantiochytrium sp. (PVTSK-03) accumulated the highest lipid content of 61.33%. Thraustochytrids were found to contain Omega-3 poly unsaturated fatty acids (PUFAs), such as EPA up to 8.89% in Aurantiochytrium sp. (VRTSK-01), DPA up to 9.65% in Aurantiochytrium sp. (AKTSK-03), and DHA up to 47.46% in Aurantiochytrium sp. (AKTSK-06). Thus, mangroves provide an ideal ecological niche for thraustochytrids with an abundant supply of omega-3 fatty acids for potential industrial applications.

Fine-tuning of key parameters to enhance biomass and nutritional polyunsaturated fatty acids production from Thraustochytrium sp

The escalating demand for long-chain polyunsaturated fatty acids (PUFAs) due to their vital health effects has deepened the exploration of sustainable sources. Thraustochytrium sp. stands out as a promising platform for omega-3 and 6 PUFA production. This research strategically optimizes key parameters: temperature, salinity, pH, and G:Y:P ratio and the optimized conditions for maximum biomass, total lipid, and DHA enhancement were 28 °C, 50 %, 6, and 10:1:2 respectively. Process optimization enhanced 32.30 and 31.92 % biomass (9.88 g/L) and lipid (6.57 g/L) yield. Notably, DHA concentration experienced a substantial rise of 69.91 % (1.63 g/L), accompanied by notable increases in EPA and DPA by 82.69 % and 31.47 %, respectively. MANOVA analysis underscored the statistical significance of the optimization process (p < 0.01), with all environmental factors significantly influencing biomass and lipid data (p < 0.05), particularly impacting DHA production. Thraustochytrium sp. can be a potential source of commercial DHA production with the fine-tuning of these key process parameters.

Nutritional enrichment of fruit peel wastes using lipid accumulating Aurantiochytrium strain as feed for aquaculture in the North-East Region of India

Utilization of fruit peel wastes to grow thraustochytrids for nutritional enrichment of wastes will lower environmental and economic costs associated with feedstock specific for aquaculture industries. In this study, high-carbohydrate content agricultural wastes, such as orange, pineapple, banana, and mausambi fruit peels were enriched with essential fatty acids producing thraustochytrids Aurantiochytrium sp. ATCC276. Characterizations of fruit peels revealed the presence of high carbohydrate content (9-16%) and reducing sugars essential for the growth of thraustochytrids. Optimization for lipid production of Aurantiochytrium sp. ATCC276 was carried out using response surface methodology (RSM) in combination with different concentrations of fruit peels in solid-state fermentation (SSF) conditions. Fruit peels composed of SSF experiments were designed using a central composite design. Aurantiochytrium sp. ATCC276 cells efficiently utilized the sugar components of fruit peels for their growth and lipid accumulation. Different SSF composites made of fruit peels were significantly enriched with fatty acids of Aurantiochytrium sp. ATCC276 cells. Culturing Aurantiochytrium sp. ATCC276 cells with these waste materials demonstrated distinct responses towards lipid accumulation at different compositions. The optimized SSF composite consists of 9.91 g 100 mL-1 orange, 5 g 100 mL-1 mausambi, 4.12 g 100 mL-1 pineapple, and 8.01 g 100 mL-1 banana peels and was enriched with 8.37% of Aurantiochytrium sp. ATCC276-derived lipids. This study expands the benefits and bioprocessing potential of essential fatty acids producing Aurantiochytrium sp. ATCC276 along with fruit peel wastes which a frontier in circular bioeconomy and valorizing waste for usage.

High cell density continuous fermentation for L-lactic acid production from cane molasses

Commercial production of lactic acid (LA) utilizes mostly glucose or lactose coupled with yeast extract (YE) as a supplement. With sugars, nitrogen, and vitamin supplementation being most of the LA production costs, the use of inexpensive molasses, a by-product of the sugar industry, can provide considerable cost savings. There are just a few publications on the production of LA from molasses; consequently, the present investigation was conducted using molasses supplemented with yeast extract. The research was done in a continuous-flow, high-cell-density (HCD) bioreactor with an external membrane microfiltration device for cell recycling. The system, run at 1 L with Lactobacillus delbrueckii NCIM 2025, produced a LA yield of 0.95-0.98 g/g from ∼100 g sugars/L when supplemented with 1 g/L YE. Dilution rates in the range of 0.04-0.36 h-1 resulted in volumetric lactic acid productivities in the range of 4.3-27.6 g/L h, which compares favorably with the highest values recorded in literature, for glucose in the presence of YE, which was as high as 30 g/L. The utilization of cane molasses has a significant impact on the economics of lactic acid production, as measured by a comparison of costs with commercial glucose.

Fermentative production of astaxanthin from sorghum distillery residue by an indigenous Aurantiochytrium sp. CJ6 strain using a continuous-feeding fed-batch process

In this study, Aurantiochytrium sp. CJ6 was cultivated heterotrophically on a waste resource, sorghum distillery residue (SDR) hydrolysate without adding any nitrogen sources. Mild sulfuric acid treatment released sugars that supported the growth of CJ6. Optimal operating parameters (salinity, 2.5%; pH, 7.5; with light exposure) determined using batch cultivation attained biomass concentration and astaxanthin content of 3.72 g/L and 69.32 µg/g dry cell weight (DCW), respectively. Using continuous-feeding fed-batch (CF-FB) fermentation, the biomass concentration of CJ6 increased to 6.3 g/L with biomass productivity and sugar utilization rate of 0.286 mg/L/d and 1.26 g/L/d, respectively. Meanwhile, CJ6 obtained maximum astaxanthin content (93.9 µg/g DCW) and astaxanthin concentration (0.565 mg/L) after 20-day cultivation. Thus, the CF-FB fermentation strategy seems to have a high potential for the cultivation of thraustochytrids to produce the high-value product (astaxanthin) using SDR as the feedstock to achieve circular economy.

Microalgal polyunsaturated fatty acids: Hotspots and production techniques

Algae play a crucial role in the earth’s primary productivity by producing not only oxygen but also a variety of high-value nutrients. One such nutrient is polyunsaturated fatty acids (PUFAs), which are accumulated in many algae and can be consumed by animals through the food chain and eventually by humans. Omega-3 and omega-6 PUFAs are essential nutrients for human and animal health. However, compared with plants and aquatic sourced PUFA, the production of PUFA-rich oil from microalgae is still in the early stages of exploration. This study has collected recent reports on algae-based PUFA production and analyzed related research hotspots and directions, including algae cultivation, lipids extraction, lipids purification, and PUFA enrichment processes. The entire technological process for the extraction, purification and enrichment of PUFA oils from algae is systemically summarized in this review, providing important guidance and technical reference for scientific research and industrialization of algae-based PUFA production.

Screening of a Thraustochytrid Strain Collection for Carotenoid and Squalene Production Characterized by Cluster Analysis, Comparison of 18S rRNA Gene Sequences, Growth Behavior, and Morphology

Carotenoids and squalene are important terpenes that are applied in a wide range of products in foods and cosmetics. Thraustochytrids might be used as alternative production organisms to improve production processes, but the taxon is rarely studied. A screening of 62 strains of thraustochytrids sensu lato for their potential to produce carotenoids and squalene was performed. A phylogenetic tree was built based on 18S rRNA gene sequences for taxonomic classification, revealing eight different clades of thraustochytrids. Design of experiments (DoE) and growth models identified high amounts of glucose (up to 60 g/L) and yeast extract (up to 15 g/L) as important factors for most of the strains. Squalene and carotenoid production was studied by UHPLC-PDA-MS measurements. Cluster analysis of the carotenoid composition partially mirrored the phylogenetic results, indicating a possible use for chemotaxonomy. Strains in five clades produced carotenoids. Squalene was found in all analyzed strains. Carotenoid and squalene synthesis was dependent on the strain, medium composition and solidity. Strains related to Thraustochytrium aureum and Thraustochytriidae sp. are promising candidates for carotenoid synthesis. Strains closely related to Schizochytrium aggregatum might be suitable for squalene production. Thraustochytrium striatum might be a good compromise for the production of both molecule groups.

Acid-assisted oil extraction directly from thraustochytrids fermentation broth and its energy assessment for docosahexaenoic acid-enriched oil production

Thraustochytrids are the most prominent source of polyunsaturated fatty acids, specifically docosahexaenoic acid (DHA). Downstream processing constitutes a significant fraction of total production cost and thus needs judicious optimization. Currently, hazardous solvent-based extraction methods are used to extract oil from the dry or wet thraustochytrids cell mass. The process is also highly energy-intensive due to involvement of dewatering and drying as unit operations. Current work devised an energy-efficient acid-assisted extraction (AAE) methodology to overcome dry and wet biomass-based extraction limitations. AAE recovered 91 % of total oil with 35-40 % PUFA from the direct fermentation broth, eliminating the need for dewatering and drying of fermentation broth/cell biomass. The current work also presents an all-inclusive comparison of the energy assessment of oil extraction from dry and AAE method. AAE produced PUFA enriched oil with a total energy consumption of 210 MJ/kg, which was four times lower than that of conventional dry cell extraction methodology.

Development and validation of reliable astaxanthin quantification from natural sources

Astaxanthin derived from natural sources occurs in the form of various esters and stereomers, which complicates its quantitative and qualitative analysis. To simplify and standardize astaxanthin measurement with high precision, an enzymolysis-based astaxanthin quantification method was developed to hydrolyze astaxanthin esters and determine free astaxanthin in all its diastereomeric forms. Astaxanthin standards and differently processed Haematococcus pluvialis biomass were investigated. Linear correlation of standards of all-E-astaxanthin was observed in a measurement range between extract concentrations of 1.0 μg/mL and 11.2 μg/mL with a coefficient of variation below 5%. The diastereomers 9Z-, and 13Z-astaxanthin, and two di-Z-forms were detected. In contrast to the measurement of standards, the observed measurement range was extended to 30 μg/mL in extracts from H. pluvialis. The nature of the sample had to be taken into account for measurement, as cell, respectively, sample composition altered the optimal concentration for astaxanthin determination. The measurement precision of all-E-astaxanthin quantification in dried H. pluvialis biomass (1.2-1.8 mg dried biomass per sample) was calculated with a coefficient of variation of maximum 1.1%, whereas it was below 10% regarding the diastereomers. Complete enzymolysis was performed with 1.0 to 2.0 units of cholesterol esterase in the presence of various solvents with up to 2.0 mg biomass (dry weight). The method was compared with other astaxanthin determination approaches in which astaxanthin is converted to acetone in a further step before measurement. The developed method resulted in a higher total astaxanthin recovery but lower selectivity of the diastereomers. The reliability of photometric astaxanthin estimations was assessed by comparing them with the developed chromatographic method. At later stages in the cell cycle of H. pluvialis, all methods yielded similar results (down to 0.1% deviation), but photometry lost precision at earlier stages (up to 31.5% deviation). To optimize sample storage, the shelf life of astaxanthin-containing samples was investigated. Temperatures below -20°C, excluding oxygen, and storing intact H. pluvialis cells instead of dried or disrupted biomass reduced astaxanthin degradation.

Optimization of Astaxanthin Recovery in the Downstream Process of Haematococcus pluvialis

Astaxanthin derived from Haematococcus pluvialis is a valuable metabolite applied in a wide range of products. Its extraction depends on a sophisticated series of downstream process steps, including harvesting, disruption, drying, and extraction, of which some are dependent on each other. To determine the processes that yield maximum astaxanthin recovery, bead milling, high-pressure homogenization, and no disruption of H. pluvialis biomass were coupled with spray-drying, vacuum-drying, and freeze-drying in all possible combinations. Eventually, astaxanthin was extracted using supercritical CO2. Optimal conditions for spray-drying were evaluated through the design of experiments and standard least squares regression (feed rate: 5.8 mL/min, spray gas flow: 400 NL/h, inlet temperature: 180 °C). Maximal astaxanthin recoveries were yielded using high-pressure homogenization and lyophilization (85.4%). All combinations of milling or high-pressure homogenization and lyophilization or spray-drying resulted in similar recoveries. Bead milling and spray-drying repeated with a larger spray-dryer resulted in similar astaxanthin recoveries compared with the laboratory scale. Smaller astaxanthin recoveries after the extraction of vacuum-dried biomass were mainly attributed to textural changes. Evaluation of these results in an economic context led to a recommendation for bead milling and spray-drying prior to supercritical CO2 extraction to achieve the maximum astaxanthin recoveries.

Production of polyunsaturated fatty acids by Schizochytrium (Aurantiochytrium) spp

Diverse health benefits are associated with dietary consumption of omega-3 long-chain polyunsaturated fatty acids (ω-3 LC-PUFA), particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Traditionally, these fatty acids have been obtained from fish oil, but limited supply, variably quality, and an inability to sustainably increase production for a rapidly growing market, are driving the quest for alternative sources. DHA derived from certain marine protists (heterotrophic thraustochytrids) already has an established history of commercial production for high-value dietary use, but is too expensive for use in aquaculture feeds, a much larger potential market for ω-3 LC-PUFA. Sustainable expansion of aquaculture is prevented by its current dependence on wild-caught fish oil as the source of ω-3 LC-PUFA nutrients required in the diet of aquacultured animals. Although several thraustochytrids have been shown to produce DHA and EPA, there is a particular interest in Schizochytrium spp. (now Aurantiochytrium spp.), as some of the better producers. The need for larger scale production has resulted in development of many strategies for improving productivity and production economics of ω-3 PUFA in Schizochytrium spp. Developments in fermentation technology and metabolic engineering for enhancing LC-PUFA production in Schizochytrium spp. are reviewed.

Bioconversion of waste acid oil to docosahexaenoic acid by integration of "ex novo'' and "de novo'' fermentation in Aurantiochytrium limacinum

Thraustochytrids have predominantly been grown on hydrophilic substrates i.e. by "de novo" fermentation. The fatty acid composition of thraustochytrids oil in "de novo" mode is enriched in saturated palmitic acid and polyunsaturated docosahexaenoic acid. The "ex novo" fermentation of a novel Aurantiochytrium limacinum ICTSG-17 with waste acid oil altered the fatty acid composition of produced oil. This led to increased total unsaturated fatty acids (TUFA) and concomitant decrease in the total saturated fatty acids (TSFA) resulting in higher TUFA/TSFA ratio. However, cell growth and DHA content in "ex novo" were lower than that of "de novo" fermentation. Integration of "de novo" and "ex novo" fermentation modes were devised to attain high biomass and lipids enriched in DHA. Sequential "de novo"-"ex novo" fermentation resulted in ~20 g/L biomass and ~40% DHA content and higher TUFA/TSFA ratio as compared to that of "de novo" mode.