An applicable nitrogen supply strategy for attached cultivation of Aucutodesmus obliquus

Abstract

The "attached cultivation" method of microalgae in which the wet paste of algal biomass is attached onto supporting materials to form an immobilized biofilm layer, and the culture medium is supplied to this layer to provide nutrients and moisture for growth was highly efficient in biomass production and represents a promising technology to improve the biofuel industry. To optimize the nitrogen supply strategy for this attached cultivation method, the growth and total lipids accumulation properties for the green alga Aucutodesmus obliquus with this method were studied under different quantities of nitrogen source and different volumes of aqueous medium that continuously circulated inside the photobioreactor. Results showed that, compared with medium volume, the nitrogen quantity was a stronger factor affecting the growth and total lipid accumulation. An optimized nitrogen supply strategy for the attached cultivation of A. obliquus is proposed as circulating ca. 60 L of BG-11 medium containing 1/10 of nitrate concentration for 1 m 2 of cultivation surface. With this strategy, the attached A. obliquus accumulated biomass and total lipids simultaneously and obtained a high triacylglyceride productivity of 2.53 g m Dissolving the nitrogen source in small volume was the best way to efficiently utilize the nitrogen source with minimum of waste.

The water footprint of biofilm cultivation of Haematococcus pluvialis is greatly decreased by using sealed narrow chambers combined with slow aeration rate

“…For the two circulating experiments, the larger the medium, the higher the final nitrate concentration in the culture broth (Table 2), similar results were also observed by Ji et al (2014). This might due to the limitation of other elements has suppressed the assimilation of nitrogen.…”

“…c o m / l o c a t e / b i o r t e c h liquid medium largely (Shi et al, 2007;Mulbry et al, 2008;Boelee et al, 2011;Naumann et al, 2013;Zamalloa et al, 2012). The primary application of this biofilm technology is limited to bioremediations of waste water in the past years until its great potentials in biomass production, light usage efficiency and water saving have been proved by a serial of our recent researches Cheng et al, 2013;Ji et al, 2014). According to these researches, the outdoor biomass productivity of a modified biofilm microalgal cultivation system, called ''attached cultivation'' system, reaches 50-80 g m À2 d…”

“…500-700% of conventional open ponds , and the water requirement is potentially reduced to <2 L for per m 2 of land area (Ji et al, 2014). This ''attached cultivation'' technology has also been successfully applied in the cultivation of Botryococcus braunii, a fascinating microalga for its ability to synthesis large quantity of hydrocarbon but very slow growth rate in suspended conditions .…”

Biofilm cultivation of the oleaginous microalgae Pseudochlorococcum sp.

“…This means that the nitrogen concentration of 8.8 mmol L -1 in the medium (half of the nitrogen concentration to standard BG11 medium) is a critical concentration for the best growth of the algal biofilm. This concentration is a little higher than that with Aucutodesmus obliquus culturing in attached biofilm style by Ji et al [26], in which one-tenth of nitrogen concentration to standard BG11 medium was enough to maintain fast growth and lipid accumulation simultaneously. Figure 6a shows the effect of phosphorous on the areal density and growth rate of Pseudochlorococcum sp.…”

Microalgae production in a biofilm photobioreactor

“…In recent years, a range of biofilm-photobioreactors were developed that intend to employ the biofilm growth as a controllable production platform of dedicated microalgal species. Examples include the twin layer system (Naumann et al 2012;Nowack et al 2005;Shi et al 2007), a similar design referred to as an attached photobioreactor (Ji et al 2013a;Ji et al 2013b), the rotating spool system (Christenson and Sims 2012), and the rotating algal biofilm cultivation system (Gross et al 2013).…”