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1 Introduction

Harvesting microalgae is an important part of microalgae cultivation system to produce high biomass (Sim et al. 1988). Centrifugation, filtration and flocculation are the most common harvesting technique used in harvesting microalgae (Grima et al. 2003; Chen et al. 2011). Centrifugation is a microalgae harvesting technique which needs high capital, energy and operating costs (Wijffels and Barbosa 2010). Harvesting microalgae using filtration technique can only be performed for microalgae species that are larger than 100 μm in size and filaments or colonized body shape, such as Spirulina sp. and Micractinium sp. (Mohn 1988). Harvesting microalgae smaller than 100 μm and not colonized can be done using flocculation. Microalgae flocculation technique will concentrate target by using chemical material (Lee et al. 1998; Papazi et al. 2010), bacteria (Choi et al. 1998; Fujita et al. 2000; Salehizaden et al. 2000; Li and Yang 2007) and fungi (Chang et al. 2005).

Harvesting microalgae using chemical flocculant is very easy to be done, but not suitable for large scale cultivation because the excessive cationic flocculants must be cleaned from the culture media so it can be re-used (Schenk et al. 2008). Flocculation using chemicals can also change the culture media conditions such as extreme pH changes, nutrient decline, and changes in temperature and dissolved oxygen. The addition of chemical compounds can also cause changes in microalgae cell composition (Benemann and Oswald 1996). Flocculation using living organisms (bio-flocculation) can be used as the alternative, so the chemical contamination effect can be reduced.

The use of fungi and bacteria as flocculants requires particular additional media as the energy source for growth. Furthermore, bacteria and fungi can cause contamination of microalgae (Schenk et al. 2008). Salim et al. (2011) stated that bio-flocculation technique using microalgae is more promising than bacteria and fungi because it does not require additional operating costs for growth media and also prevents contamination. The most important thing from using microalgae for bio-flocculation is it is environment friendly because it does not use chemicals and the cultivation media can be re-used.

Bio-flocculation technique can be used as an alternative method for microalgae harvest. It is urgent to...

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