The efficiency of harvesting C. vulgaris with iron oxide magnetic microparticles is comparable with other magnetic microalgae separation procedures. From
the highly diluted culture broth, thick-magnetized microalgal slurry was obtained
within minutes, while a complete demagnetization of cells was achieved within
1 h, if necessary. Consequently, the separation efficiencies depend upon culture
medium composition and microalgae species (Prochazkova et al. 2013).
Ultrasound This separation process is based on gentle acoustically induced
aggregation followed by enhanced sedimentation. Testing the microalgae
Monodus subterraneus, Bosma et al. (2003) got a harvest efficiency of more than
92 %. On the industrial scale, centrifuges can be better used to harvest microalgae
because of lower power consumption, better efficiency, and higher concentration
factors. In laboratory or pilot plant scale, the ultrasonic harvesting process has the
advantages of being operated continuously, evokes no shear stress, and the
occupation space is very small. Also, it never gets blocked with cells; cells are still
viable, because no shear stress is involved. This means the harvested biomass can
be used as inoculums or can still be investigated by analytical techniques. When an
organism excretes a high valuable secondary metabolite, this technique can be
used as a retention system. The resonation chamber acts as a biological filter by
rejecting the organisms and allowing the solubilized product to pass. Higher
biomass concentrations can be reached inside the bioreactor and the concentration
of the desired product will rise (Bosma et al. 2003).
8.6 Future Prospects
Microalgae are an excellent biological resource and one of the most promising
sources for new products and applications (Pulz and Gross 2004). They can be
used to enhance the nutritional value of food and animal feed due to their wellbalanced chemical composition. Microalgae cultures are better in relation to
agricultural crops as they do not need enormous extensions of fertile ground,
present low dependence of climatic swaying, are a good possibility for biofuels
production, are a good atmospheric carbon tramp, and are good alternatives for
high-value biological co-products.
Although work with microalgae and production systems has increased and is
running successfully in many parts of the world, especially in Asia, further
research work is needed to close the gap between possible low-cost bulk production like food, feed, or biofuels using microalgae. Till now, only high-value
products are produced using microalgae. Partly due to this, development in lowcost production systems is slow. For producing high-value products there is no
need to lower production costs significantly. However, to really take advantage of
all benefits that algae have it is necessary to create lower cost production plants
and also be able to obtain all available products. Lower cost production can be
achieved by producing microalgae in controlled environments where production
efficiency can be increased and less man-hours are needed; higher efficiency will
8 Microalgae and Cyanobacteria Production for Feed and Food Supplements
271
the highly diluted culture broth, thick-magnetized microalgal slurry was obtained
within minutes, while a complete demagnetization of cells was achieved within
1 h, if necessary. Consequently, the separation efficiencies depend upon culture
medium composition and microalgae species (Prochazkova et al. 2013).
Ultrasound This separation process is based on gentle acoustically induced
aggregation followed by enhanced sedimentation. Testing the microalgae
Monodus subterraneus, Bosma et al. (2003) got a harvest efficiency of more than
92 %. On the industrial scale, centrifuges can be better used to harvest microalgae
because of lower power consumption, better efficiency, and higher concentration
factors. In laboratory or pilot plant scale, the ultrasonic harvesting process has the
advantages of being operated continuously, evokes no shear stress, and the
occupation space is very small. Also, it never gets blocked with cells; cells are still
viable, because no shear stress is involved. This means the harvested biomass can
be used as inoculums or can still be investigated by analytical techniques. When an
organism excretes a high valuable secondary metabolite, this technique can be
used as a retention system. The resonation chamber acts as a biological filter by
rejecting the organisms and allowing the solubilized product to pass. Higher
biomass concentrations can be reached inside the bioreactor and the concentration
of the desired product will rise (Bosma et al. 2003).
8.6 Future Prospects
Microalgae are an excellent biological resource and one of the most promising
sources for new products and applications (Pulz and Gross 2004). They can be
used to enhance the nutritional value of food and animal feed due to their wellbalanced chemical composition. Microalgae cultures are better in relation to
agricultural crops as they do not need enormous extensions of fertile ground,
present low dependence of climatic swaying, are a good possibility for biofuels
production, are a good atmospheric carbon tramp, and are good alternatives for
high-value biological co-products.
Although work with microalgae and production systems has increased and is
running successfully in many parts of the world, especially in Asia, further
research work is needed to close the gap between possible low-cost bulk production like food, feed, or biofuels using microalgae. Till now, only high-value
products are produced using microalgae. Partly due to this, development in lowcost production systems is slow. For producing high-value products there is no
need to lower production costs significantly. However, to really take advantage of
all benefits that algae have it is necessary to create lower cost production plants
and also be able to obtain all available products. Lower cost production can be
achieved by producing microalgae in controlled environments where production
efficiency can be increased and less man-hours are needed; higher efficiency will
8 Microalgae and Cyanobacteria Production for Feed and Food Supplements
271