Thraustochytrids in aquaculture: Can it replace fish meal in Aquafeed?

Global fish production peaked at about 171 million tonnes in 2016, with aquaculture contributing 47 percent (80million tonnes) to the total.While capture fishery production remains static since the 1980s, aquaculture production is rapidly growing and is now almost on par with the capture fishery. The growth of the aquaculture sector is also faster than other major food production sectors registering a 5.8 percent annual growth rate during the period 2001–2016. In 2016, of the total fish production, 12 percent (about 20 million tonnes) was used for non-food purposes. A greatest part of these (74 percent or 15 million tonnes) was reduced to fishmeal and fish oil, while the rest (5 million tonnes) was largely utilized as material for direct feeding in aquaculture and raising of livestock and fur animals, in culture, as bait, in pharmaceutical uses and for ornamental purposes. About 220 aquatic animals and plants species are cultured around the world, in a vast range of production systems. Generally aquaculture production systems can be divided into feed-dependent systems or fed aquaculture (e.g. finfish and crustaceans) or non-fed aquaculture systems where culture is predominately dependent on the natural environment for food, e.g. aquatic plants and molluscs

Overview of systematics, morphology, biodiversity and potential utilisation of Thraustochytrids

Thraustochytrids, heterotrophic protists were first reported in 1934 and then on several isolates were reported across the world and their advantageous and harmful properties have been explored and utilised. They are oleaginous saprophytic marine heterokontophytes and are emerging as an alternative oil source in pharmaceutical and aquaculture industries. These are known for their role in marine food web and nutritional recycling and are commercially exploited for their ability to produce abundant nutraceutical fatty acids, particularly long-chain poly unsaturated fatty acids such as docosahexaenoic acid, eicosapentaenoic acid and squalene. This review gives an insight on the available information on taxonomy, morphology, biodiversity and utilisation of Thraustochytrids and also identifies the knowledge gap and understanding in the field of Thraustochytrids and their importance in polyunsaturated fatty acids enriched commercial products

Dietary supplementation of microalgae, Aurantiochytrium sp. and co-feeding with Artemia enhances the growth, stress tolerance and survival in Penaeus monodon (Fabricius, 1798) post larvae

In global aquaculture industry, shrimp farming plays a key role and microalgae signify a vital part. The present study focussed to analyse the influence of dietary inclusion of Aurantiochytrium sp. MBTDCMFRIJMVL1, a heterotrophic marine protist as well as co-feeding with Artemia, on the growth and survival in black tiger shrimp (Penaeus monodon). The nutritive quality, with a total protein content of 54% and total fat content of 26% on dry matter basis along with good fatty acid profile and carotenoids makes Aurantiochytrium sp. a promising candidate for aquaculture nutrition. In the present study, three type of micro diets were designed (iso11-nitrogenous and isolipidic) with 50% crude protein and 8% crude fat viz., control diet (C), 1% inclusion of algae (T1) and 2% inclusion of algae (T2) and fed to the post larvae (PL) of P. monodon. There were six treatments in triplicate as follows; control (C), control accompanied by co-feeding with Artemia nauplii (C + A), 1% dietary inclusion of algae (T1), T1 with co-feeding (T1 + A), 2% dietary inclusion of algae (T2) and T2 along with co-feeding (T2 + A). 3600 numbers of PL with average length and weight 4.98 ± 0.13 mm and 1.51 ± 0.05 mg, respectively were randomly stocked in 18 rectangular glass tanks of 20 L water holding capacity with 200 PL in each tank and maintained at a salinity of 25‰. After the experimental period of 28 days, a better growth performance, survival rate, stress tolerance, nutritional quality and metabolic enzyme profile of the larvae were observed in ‘T2 + A' when compared to other treatments, while the lowest performance was observed in ‘C'. This study also concluded that, co-feeding with Artemia greatly enhanced the improvements brought by algal supplementation. Algal supplementation in the micro diet of P. monodon improved disease resistance against Vibrios. The fatty acid profile of PL28 were influenced due to algal supplementation. The levels of palmitic acid and docosahexaenoic acid (DHA) were higher and significantly different (P < 0.05) in P. monodon fed with algal supplemented diet, which reflected the fatty acid profile of Aurantiochytrium sp. This experiment revealed that dietary incorporation of Aurantiochytrium sp. at 2% level can significantly improve the growth, survival, nutritional quality and tolerance to stress in P. monodon post larvae suggesting its potential application in aquaculture

Isolation and phylogenetic identification of heterotrophic thraustochytrids from mangrove habitats along the southwest coast of India and prospecting their PUFA accumulation

Among several sustainable resources, marine heterotrophic microorganisms have gained much interest for various commercial applications owing to their potential to produce high quantities of polyunsaturated fatty acids. Above 70% of the globally produced fish oil is utilised for aqua feed formulations. Intense research is being carried out to find suitable alternatives to fish oil. Oleaginous protists are being explored as a promising substitute to fish oil and also for various high-value-added products. However, characterisation and utilisation of these unique protists remain underexplored in many countries including India and this prompted us to screen and isolate these heterotrophic microorganisms capable of producing PUFAs. In this study, 11 strains of heterotrophic thraustochytrid capable of producing significant quantities of polyunsaturated fatty acids were successfully isolated from different mangrove habitats along the southwest coast of India. Morphological characterisation along with molecular identification revealed that these strains showed close similarity to Aurantiochytrium spp. of the family Thraustochytridae. They are able to produce 7–11 g of dry biomass per litre of culture. Their fatty acid content was up to 12%(wt/wt) of biomass and GC analysis confirmed that these protists can accumulate docosahexaenoic acid as high as 22–60% of the total fatty acids. Their enzymatic activity, tolerance to various abiotic stress factors and antagonistic potential against vibrios are also described. These heterotrophic protists can antagonise aquaculture pathogens and act as an excellent source of docosahexaenoic acid that indicates their potential as a sustainable alternative to fish oil

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Not AvailableAmong several sustainable resources, marine heterotrophic microorganisms have gained much interest for various commercial applications owing to their potential to produce high quantities of polyunsaturated fatty acids. Above 70% of the globally produced fish oil is utilised for aqua feed formulations. Intense research is being carried out to find suitable alternatives to fish oil. Oleaginous protists are being explored as a promising substitute to fish oil and also for various high-value-added products. However, characterisation and utilisation of these unique protists remain underexplored in many countries including India and this prompted us to screen and isolate these heterotrophic microorganisms capable of producing PUFAs. In this study, 11 strains of heterotrophic thraustochytrid capable of producing significant quantities of polyunsaturated fatty acids were successfully isolated from different mangrove habitats along the southwest coast of India. Morphological characterisation along with molecular identification revealed that these strains showed close similarity to Aurantiochytrium spp. of the family Thraustochytridae. They are able to produce 7–11 g of dry biomass per litre of culture. Their fatty acid content was up to 12% (wt/wt) of biomass and GC analysis confirmed that these protists can accumulate docosahexaenoic acid as high as 22–60% of the total fatty acids. Their enzymatic activity, tolerance to various abiotic stress factors and antagonistic potential against vibrios are also described. These heterotrophic protists can antagonise aquaculture pathogens and act as an excellent source of docosahexaenoic acid that indicates their potential as a sustainable alternative to fish oil.Not Availabl

Exploration of seaweed degradation potential of the prioritized microbes as a green saccharification technology

A novel pretreatment process based on prioritized microbes was developed to improve the yield of reducing sugars from red (Gracilaria corticata), brown (Sargassum wightii), and green (Ulva fasciata) seaweeds as a cheap, eco-friendly method for seaweed saccharification. Prioritization of six microbes from a collection of 24 microbes was initially done using a unique stepwise strategy considering different polysaccharides present in varied seaweed types. Final selection of three microbes was based on the release of reducing sugars from different seaweed groups in the saccharification process. The selected microbes significantly increased the release of reducing sugars compared to the control conditions in all three seaweed species, with significant differences (P<0.05) based on the media, microbes, seaweed species, processed condition, and days of hydrolysis. Factor analysis of mixed data indicated that microbes contributed to the maximum variability of the data. Vibrio parahaemolyticus caused the maximum biomass conversion ratio for reducing sugars from S. wightii (22.31 ± 0.65%) and U. fasciata (24.6 ± 1.28%) with an increment of 8.9% and 9.35%, respectively from control conditions. The maximum biomass conversion of G. corticata was 24.8 ± 0.51% following Bacillus amyloliquefaciens treatment with an increment of 6.39% from the control. Even though different combinations of three prioritized microbes produced better saccharification than the control conditions, individual use of prioritized microbes made a better release of reducing sugars. In brief, seaweed hydrolysis using the prioritized microbes of the present study can be applied to improve the saccharification process of seaweeds in an eco-friendly and less expensive platform

Comparative study on pre-treatment methods for enhanced saccharification from tropical seaweeds to aid in bioethanol production

The selection of suitable pretreatment strategy that facilitates saccharification is the most critical step in the valorisation of seaweed biomass into bioethanol. Considering the scarcity of data on the comparative efficacy of different pretreatments particularly in tropical seaweed species, 50 pretreatment strategies were analysed on three major species representing all the three broad seaweed categories, viz. Ulva fasciata (green algae), Sargassum wightii (brown algae), and Gracilaria corticata (red algae). An improved release of reducing sugars was observed in all the tested pretreatments, with different conversion ratios for different species in each pretreatment. Ultrasonication and magnetic stirring showed maximum yield among physical pretreatments. In thermal methods, microwave oven incubation resulted in maximum yield from both U. fasciata and S. wightii, while it was autoclaving for G. corticata. Sulphuric acid was the best chemical for U. fasciata and G. corticata, while it was orthophosphoric acid for S. wightii. Hydrochloric acid was the best chemical for physicothermochemical pretreatment in all species. Maximum conversion ratios of 2.58, 2.11, and 2.0 were recorded in U. fasciata, G. corticata, and S. wightii respectively. In short, the paper sketches the best pretreatment method for three major tropical seaweeds along with their proximate composition. The results can be applied for aiding the valorisation of biomass of these seaweeds through a cost-effective manner