Microalgae Paste as an Alternative Feed Ingredient

Soledad S. Garibay Institute of Aquaculture, College of Fisheries and Ocean Sciences

U.P. Visayas, Miagao, Iloilo

Telefax: 033-3158090/E-mail: ssgaribay@up.edu.ph/sgaribay009@gmail.com

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I. Introduction

Microalgae, considered as one of the tiniest plants (Ugoala, et al, 2012) produces about

60% of Earth’s oxygen. These constitute around 25,000-30,000 species in a very diverse forms

and sizes. These organisms produce protein and energy 30-100 times faster than land plants.

Microalgae are small unicellular plants that can be found in freshwater, marine and

brackishwater, and even in damp terrestrial areas. Over the years, it has always been there and

considered to have myriads of potential uses. These are very important both in aquaculture and

mariculture as natural food for zooplankton which are then being fed to fish larvae and

crustacean zoea (McVey et al, 1993). Microalgae are not only utilized in aquaculture but are

also being used as human food, fuel, fiber, pharmaceuticals, fertilizers and organic chemical

feedstock (Enzing et. al, 2012; Marcus, 2009; De Jesus and Ruiz, 2009), thus, the demand for

algae is increasing worldwide. The producers therefore require the development of technologies

to reduce the cost production and meet the demand while maintaining and improving the product

quality.

Aquaculture contributes to the 40% fish production in the Philippines from 226,195

aquaculture operators (FAO-UN, 2002). Given this number of fish farmers in the country,

continuous supply of natural food and live microalgae is expected. However, microalgae cultures

have stability issues due to its weather sensitivity.

The commercialization of microalgae has been recognized in the production of nutritional

supplements, antioxidants, cosmetics, natural dyes and polyunsaturated fatty acids (PUFA)

(Spolaore et al., 2006). The major factors that determine the nutritional value of microalgae are

the protein and vitamin content as well as the polyunsaturated fatty acid like eicosapentaenoic

acid (EPA), arachidonic acid (AA) and docosahexaenoic acid (DHA). Because of its nutritional

potentials, the mass production of certain protein-rich microalgae is being considered as an

alternative feed ingredient to other protein sources. Comprehensive analyses and nutritional

studies have demonstrated that algal proteins from microalgae are of high quality and

comparable to conventional vegetable proteins. However, because of high production costs as

well as technical difficulties to incorporate the algal material into palatable food preparations, the

propagation of algal protein is still in its infancy.

For lipid component, several strategies are being practiced to manipulate the lipid

composition and overall yield of microalgae production. These include the light intensity,

nutrient and temperature (Catarina et al., 2010). For culture, microalgae strains to be selected

should have the ease of culturing, lack of toxicity, high nutritional value with correct cell size

and shape and a digestible cell wall for the availability of nutrients (Raja et al. 2004; Patil et al.,

2007). In aquaculture, among the most frequently used species of microalgae that possess such

qualities include the Tetraselmis, Chaetoceros and Nannochloropsis (Spolaore et al., 2006).

Currently, through the UPV-DOST-PCAARRD Program those microalgae species including

Chlorella vulgaris have been successfully produced and developed in the form of algal paste.

These are the four major species that are presently being studied under the National Aquafeeds

R&D Program at the U.P.Visayas, Miagao, Iloilo and U.P. Los Baṅos, Laguna in collaboration

with SEAFDEC AQD., Tigbauan, Iloilo.

Tetraselmis are excellent feed for larval shrimps and contains natural amino acids that

stimulate feeding in marine animals. This could be used together with Nannochloropsis for

producing rotifers, a good size for feeding brine shrimp, standard feed for oysters, clams,

mussels, and scallops. This is also an excellent feed for increasing growth rates and for fighting

zoea syndrome (Hemaiswarya et al., 2010). Some Chaetoceros strains are being used to increase

the vitamin levels in shrimp hatcheries. Chlorella vulgaris, a freshwater microalgae species is

also widely used as feed for freshwater finfish and bivalve species.

Microalgae pastes have been commercially produced in different countries such as in the

USA, Canada, United Kingdom and other places but costs of shipment and time factor in terms

of delivery have to be considered.

The Philippine algal paste or concentrate produced through the National Aquafeeds R&D

Program was proved to be an effective alternative for live microalgae based on the experiments

conducted. The nutritional profile and enrichment values of these products are currently being

investigated. The protocol for production has already been established and it is now being tested

in hatcheries in collaboration with other private hatcheries and academe in the country.

This lecture is purposely presented to encourage academician and researchers to work on

microalgae because of its importance and potentials as an alternative feed ingredient for future

research endeavors.

II. Microalgae and its Importance

Microalgae are so small yet the dynamics of its existence in a system still has to be fully

understood and investigated. In many cases, its presence in a system has contributed a lot as

manifested on the organisms such as: stabilizing the water quality in static rearing systems

(remove metabolic by-products, produce oxygen), or as conditioning effect to organisms, serves

as a direct food source through active uptake by the larvae with the polysaccharides present in

the algal cell walls possibly stimulating the non-specific immune system in the larvae. It is also

an indirect source of nutrients for fish larvae through the live feed (i.e. by maintaining the

nutritional value of the live prey organisms in the tank). Microalgae in a system increases

feeding incidence by enhancing visual contrast and light dispersion and acts as microbial control

by algal exudates in tank water and/or larval gut.

A. As Live Feed

Live microalgae are one of the important factors in the larval feeding of fish, shrimp and

bivalves. They are naturally occurring, single-celled organisms capable of converting sunlight

and simple nutrients into energy. The conventional method of culture has been in place for years.

However, the process of culturing live microalgae has disadvantages: 1) expensive 2) time

consuming 3) labour intensive and prone to crashing and 4) production requires more space for

culture and 5) difficult to incorporate to feed. Hatcheries have to grow their own microalgae on-

site in specially built, expensive facilities due to unavailability of commercial source of

microalgae. With that, alternative to growing microalgae is focused on algal paste production.

B. Microalgae in Paste Form

While questions on method how to incorporate microalgae to feed , microalgal pastes

production came to view. Algae Pastes are a super-concentrated liquid microalgae feed for

larval fish, shrimp and bivalve shell fish. It is made from microalgae grown intensively in large

industrial facilities but concentrated by removing most of the water. Microalgae pastes are now

commercially produced. These pastes are used to supplement or replace live algae grown on-site

at the hatchery. Several advantages of using Microalgae Pastes are listed as follows:

1) As live algae replacement – use of microalgae paste reduces the risks of losing feed because

microalgae paste can be used directly as primary feed or as backup in case algae culture

collapses.

2) Reduce overhead and production costs - less electricity, less space, fewer technicians.

3) Reduce live food production space - live algae systems need a lot of space that could be used

for growing your target animals.

4) Easy to Use liquid concentrate - use only the amount of algae you need at each feeding.

5) Relatively long Shelf Life - 8 to 12 weeks in the refrigerator (depending on the culture).

Nannochloropsis, Chaetoceros calcitrans and Tetraselmis can be frozen for long life and can be

made available year round.

6) Can be used as inoculum -- results of UPV algae paste studies conducted proved that one to

two month-old paste can still be used as starter or inoculum to begin a new culture cycle

provided with good illumination.

C. For Enrichment of Zooplanktons

Pavlova is a small golden/brown flagellate that is very similar to Isochrysis. It has a very

high DHA profile and is excellent for enriching rotifers and other zooplankton. The slow

motility of these organisms has contributed to their usefulness as good prey for active

larvae

Tetraselmis is a large green flagellate with a very high lipid level. It also contains natural

amino acids that stimulate feeding in marine animals. It is an excellent feed for larval

shrimp.

Nannochloropsis is a small green alga that is extensively used in the aquaculture industry

for growing small zooplankton such as rotifers and for Greenwater. It is also used in reef

tanks for feeding corals and other filter feeders.

Isochrysis is a small golden/brown flagellate that is very commonly used in the

aquaculture industry. It is high in DHA and often used to enrich zooplankton such as

rotifers or Artemia.

Thalassiosira weissflogii is a large diatom that is used in the shrimp and shellfish

larviculture industry. This alga is considered by several hatcheries to be the single

best algae for larval shrimp.

Chaetoceros calcitrans, another diatom that belongs to the Bacillariphyceae group is

another species of microalgae that is commonly used in hatcheries either fed directly to

shrimp zoea or as feed for rotifers.

D. As Livestock Feed

Algae Suspension for Livestock Production - Although the mechanism has not been

understood yet, algal suspension appeared to improve the balance of nutrients in a straw-

based diet and thus increased the efficiency of conversion of feed to products (Tareque and

Saadullah 1988). The introduction of algal suspension in the feeding system would certainly

help economic livestock production. Many livestock farmers, particularly in the urban and

suburban areas, raise their animals absolutely on straw and concentrate with either very little

or no green grasses. This system of feeding is often associated with infertility, night

blindness or even total blindness or other symptoms of vitamin A deficiency. Algae are a

very rich source of carotene and algal suspension could be a potential source of vitamin A to

combat such deficiencies.

III. Microalgae Paste Production Systems

Microalgae Paste is a slurry of concentrated microalgae cells, cultured by the batch

system in mono-specific cultures.

The culture batches are continuously monitored for quality control, and when they are in

log growth phase and are at their nutritional peak they are concentrated by high volume

Cells are flocculated using chemical and electrolytic method

Concentrated cells are allowed to settle to remove water

Excess water is removed further; microalgae cells are collected and harvested as paste.

IV. Storage and Preservation Methods

To provide a longer viability, microalgae paste can be stored under refrigerated

conditions for three months. Addition of food grade preservative will also provide a relatively

long shelf-life. Microalgae paste in frozen algae cube proves to prolong the shelf-life of the

microalgae paste however, the consistency and suspension ability is reduced.

V. Proximate Composition of Microalgae Paste (Aquafeeds Project,UPV)

Table 1. Comparison of Proximate composition (dry basis) of the samples, after 2 weeks and

after 26 weeks of storage with commercial microalgae paste and typical seafood

1 --- Electrolytic method

2 --- Chemical method

Comparison of the proximate composition of the samples with the commercial algal paste

(REED Mariculture) show that the samples is comparable in terms of moisture content or dry

weight and crude lipid, but much lower protein content and much higher ash content. During

storage, gradual liquefaction is evident for all samples as reflected in the decrease in % dry

matter and its physical appearance and loss in viscosity. For all samples, protein and crude fat in

electrolytic coagulated samples is higher.

III. Application of Microalgae Paste to Culture

1. By gravity flow (easy and inexpensive)

Hang the bucket slightly above tank

Use a thin plastic tube to siphon the algae from the bucket into the tank

Use a clip to regulate the flow of algae so it will run for a full day at a constant drip

In warm environments add a frozen "gel ice" to the bucket to keep the algae

concentrate cool

2. By dissolving the paste

Scoop a small amount of microalgae paste (depending on the desired algal density)

Mixed in the culture medium (freshwater or seawater depending on the species used)

until completely dissolved

Aerate for a few minutes to keep the microalgae in suspension and its ready to use

IV. Prominent Companies Producing Microalgae Feed Additives

1. Reed Mariculture, a company based in the United States that produces microalgae paste

for aquaculture purposes.

2. Cyanotech produces products from microalgae grown at its 90-acre facility in Hawaii,

United States, using patented and proprietary technology and distributes them to

nutritional supplement, nutraceutical, cosmeceutical, and animal feed makers and

marketers in more than 40 countries worldwide.

3. Ingrepro BV - Ingrepro turns algae into dozens of products, from horse feed to weed

killer for golf courses. As a food additive for humans, it is a source of healthy omega-3

fatty acids.

4. Sun Chlorella - Established in 1969, Sun Chlorella has 32 corporate offices located

throughout Japan, the U.S., Europe and Asia, reaching customers worldwide

with Microalgae nutrition products.

V. Future Research

The use of microalgae paste as feed ingredient or as an additive commands

undertaking requiring more research efforts to deal with. To incorporate the paste in a

more palatable or acceptable form that can be utilized for either aquaculture or livestock

needs further investigations.

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