pocketz.doi.bio/2026-02-26_102237_sciencedirectcom_S2211926415300394

Raw dark fermentation effluent to support heterotrophic microalgae growth: microalgae successfully outcompete bacteria for acetate - ScienceDirect

URL: https://www.sciencedirect.com/science/article/abs/pii/S2211926415300394

Saved: 2026-02-26T18:22:37.700Z

Algal Research Volume 12, November 2015, Pages 119-125 Raw dark fermentation effluent to support heterotrophic microalgae growth: microalgae successfully outcompete bacteria for acetate Author links open overlay panel V. Turon a , E. Trably a , A. Fayet a , E. Fouilland b, J.-P. Steyer a Show more Add to Mendeley Share Cite https://doi.org/10.1016/j.algal.2015.08.011 Get rights and content Highlights • Microalgae can outcompete dark fermentation bacteria for acetate uptake. • Butyrate is not used by Chlorella sorokiniana in heterotrophic conditions. • Bacteria originating from dark fermentation effluent can degrade butyrate. ABSTRACT Coupling dark fermentation (DF), which produces hydrogen from diverse effluents or solid waste, and heterotrophic cultivation of microalgae, which produces lipids, carbohydrates and proteins, is a promising and innovative solution for developing sustainable biorefineries. The use of a raw DF effluent, containing acetate and butyrate, to support the heterotrophic growth of Chlorella sorokiniana was investigated. All the acetate in sterilized and unsterilized DF effluent was exhausted in less than three days of heterotrophic cultivation, whereas butyrate was not used by the microalgae. The microalgae biomass reached 0.33 g L− 1 with a carbon yield on acetate of 55%. The algal yield was higher than previously reported for synthetic DF effluent. It was concluded that compounds other than volatile fatty acids were present in the DF effluent and these could be consumed by the microalgae. After the acetate had been exhausted, butyrate was consumed by facultative and strict aerobic bacteria originating from the DF effluent. The concentration of the bacterial community increased during the experiment but did not have any significant impact on heterotrophic microalgae growth. A high microalgal biomass yield was achieved without requiring the DF effluent to be sterilized. Graphical abstract Download: Download high-res image (312KB) Download: Download full-size image Introduction Over the past decade, increasing attention has been paid to the growth of microalgae in heterotrophic conditions, i.e. in the dark using organic carbon sources, due to (i) high growth rates, biomass densities and lipid yields achieved, (ii) the possibility of using non-arable land, (iii) high volumetric production and (iv) the use of existing technologies, such as microbial fermenters [1]. Heterotrophic microalgae can be cultivated to produce either low-added value molecules such as lipids for biofuels, or high-added value molecules such as the omega 3 fatty acids, DHA and EPA, for human nutrition [2]. However, owing to the high cost of the most common substrate, glucose, using heterotrophic microalgae is only currently economically competitive for human nutrition [3]. In recent years, coupling bacterial dark fermentation (DF), to produce hydrogen, and heterotrophic cultivation of microalgae, to produce lipids, has been suggested as being a very promising sustainable approach for producing gaseous and liquid biofuels [4]. DF is a simple process that can convert a wide range of solid waste and effluents into hydrogen, a high-energy gas [5]. During DF, anaerobic bacteria break down complex carbon compounds from the organic matter contained in waste (e.g., food waste or agricultural waste) and wastewater (e.g., wastewater from agriculture, the paper industry or the sugar industry) into simple organic acids [6]. Acetic and butyric acids are the two main end products of DF and can be further used as low cost carbon sources to sustain the growth of heterotrophic microalgae [7]. The main advantage of DF is that organic carbon compounds from complex waste that are not directly available to microalgae degradation are simplified into low molecular weight volatile fatty acids (VFAs) [8]. DF effluents also contain substantial amounts of nitrogen and phosphorus that are required to sustain the heterotrophic growth of microalgae. Cho et al. pointed out that DF effluent can be regarded as a good medium for growing heterotrophic microalgae in a biorefinery [9]. Recent studies investigating microalgae growth on a synthetic DF effluent medium showed very promising results. When grown heterotrophically on a mixture of acetate and butyrate, Chlorella protothecoides reached a carbon yield (g carbon of biomass per g carbon of VFAs) of 34% and a lipid content of 48% of cellular dry weight (CDW) [3]. Turon et al. [10] reported that Chlorella sorokiniana could grow heterotrophically on acetate with a growth rate of 2.23 d− 1 and a carbon yield of 42% and on butyrate with a much lower growth rate of 0.16 d− 1 and a carbon yield of 56%. Recent studies showed that heterotrophic microalgae growth was possible using sterilized DF effluents. For example, heterotrophic Scenedesmus sp. produced lipids up to 41% of CDW using acetate from sterilized DF effluent containing ethanol but no butyrate [7]. Chlorella vulgaris was grown in heterotrophic conditions on diluted DF effluent containing acetate and butyrate, converting VFAs efficiently into carbohydrates (51% CDW) [11]. Furthermore, Chlorella sp. was recently reported to produce lipids up to 26% of CDW under mixotrophic conditions with raw DF effluent as a medium [12]. For both raw and synthetic effluents, butyrate concentration has been identified as a key factor driving the effective coupling of DF and heterotrophic cultivation of microalgae under heterotrophic or mixotrophic conditions. Although acetate can be efficiently converted into lipids, butyrate uptake by microalgae is much slower and can reduce the microalgae growth when both VFAs are present. This problem can be solved either by increasing the initial microalgae biomass or by increasing the initial acetate:butyrate ratio [11], [13]. To couple DF and heterotrophic cultivation of microalgae efficiently, the cost of effluent sterilization has to be reduced. According to Park et al., sterilization of the medium accounts for more than a quarter of the investment cost of the process when coupling DF and oleaginous yeast cultivation [4]. The importance of being able to use an unsterilized medium to support microalgae growth was also emphasized by Ramos Tercero et al. [14]. Bacterial contamination is one of the main challenges to be faced for upscaling heterotrophic cultivation [15]. During heterotrophic cultivation, the competition between microalgae and bacteria is usually found to be unfavorable to microalgae, limiting the availability of carbon, nitrogen, phosphate and oxygen [16], [17]. Nevertheless, these authors suggested that some conditions may be favorable to microalgae growth, such as a low initial bacterial density and high initial nutrient loads. This work set out to determine, for the first time, the role and importance of the bacterial community present in raw DF effluent on microalgae growth for coupling DF and microalgal heterotrophic cultivation. C. sorokiniana was used as a model for heterotrophic microalgae because of its high growth rate on acetate and its ability to produce high amounts of lipids up to 61.5% of its CDW [10], [18]. The dynamics of biomass growth and carbon yield of C. sorokiniana were evaluated using sterilized and unsterilized, raw DF effluent and the biomass and diversity of bacterial community originating from the DF effluent were evaluated for the unsterilized DF effluent. Access through your organization

Check access to the full text by signing in through your organization.

Access through your organization Section snippets Dark fermentation test batches Five identical test batches of “DF effluent” were produced simultaneously in 600 mL glass bottles with a working volume of 200 mL. No culture medium was added or removed during the fermentation. The culture medium consisted of 100 mM of 2-(N-morpholino) ethanesulfonic acid (MES) buffer, 5 g L− 1 of glucose and 5 mL L− 1 of a micronutrient solution. The composition of the micronutrient solution is fully described by Pierra et al. [19]. The medium was supplemented with 1 mL L− 1 of F/2 medium vitamin Dark fermentation test batches DF anaerobic test batches were carried out to provide a culture medium for subsequent heterotrophic microalgae growth. The fermentation ended with complete glucose exhaustion, after 6 days of fermentation. The final acetate and butyrate concentrations were 1.09 ± 0.09 g L− 1 and 1.43 ± 0.07 g L− 1, respectively. No other fermentation metabolites, i.e. lactate, ethanol, propionate, valerate and caproate, were found. The hydrogen yield, i.e. the molar ratio of hydrogen produced per mol of glucose consumed, Conclusions This study showed the feasibility of using unsterilized dark fermentation effluent for heterotrophic cultivation of microalgae. Microalgae successfully outcompeted bacteria originating from DF effluent for acetate and achieved a carbon yield of 55%. The butyrate concentration was too high to support microalgae growth but can be degraded by the aerobic bacterial species initially present in the raw DF effluent. The use of a fed-batch mode for heterotrophic cultivation of microalgae using raw DF Acknowledgments This study was funded by the National Institute of Agronomic Research (INRA) and the University of Montpellier II, France. References (46) S. Venkata Mohan et al. Heterotrophic microalgae cultivation to synergize biodiesel production with waste remediation: progress and perspectives Bioresour. Technol. (2015) G. Markou et al. Microalgae for high-value compounds and biofuels production: a review with focus on cultivation under stress conditions Biotechnol. Adv. (2013) C. Sambusiti et al. Algae as promising feedstocks for fermentative biohydrogen production according to a biorefinery approach: a comprehensive review Renew. Sust. Energ. Rev. (2015) W.S. Lee et al. A review of the production and applications of waste-derived volatile fatty acids Chem. Eng. J. (2014) H.-Y. Ren et al. Enhanced energy conversion efficiency from high strength synthetic organic wastewater by sequential dark fermentative hydrogen production and algal lipid accumulation Bioresour. Technol. (2014) V. Turon et al. Use of fermentative metabolites for heterotrophic microalgae growth: yields and kinetics Bioresour. Technol. (2015) C.-H. Liu et al. Biohydrogen production by a novel integration of dark fermentation and mixotrophic microalgae cultivation Int. J. Hydrog. Energy (2013) B. Hu et al. Development of an effective acidogenically digested swine manure-based algal system for improved wastewater treatment and biofuel and feed production Appl. Energy (2013) M. Moon et al. Mixotrophic growth with acetate or volatile fatty acids maximizes growth and lipid production in Chlamydomonas reinhardtii Algal Res. (2013) N. Rashid et al. Current status, issues and developments in microalgae derived biodiesel production Renew. Sust. Energ. Rev. (2014) View more references Cited by (61) Valorization of volatile fatty acids derived from low-cost organic waste for lipogenesis in oleaginous microorganisms-A review 2021, Bioresource Technology Show abstract Resource recovery from wastewaters using microalgae-based approaches: A circular bioeconomy perspective 2020, Bioresource Technology Show abstract Waste biorefineries — integrating anaerobic digestion and microalgae cultivation for bioenergy production 2018, Current Opinion in Biotechnology Show abstract Bio-hythane production from microalgae biomass: Key challenges and potential opportunities for algal bio-refineries 2017, Bioresource Technology Show abstract Potentialities of dark fermentation effluents as substrates for microalgae growth: A review 2016, Process Biochemistry Citation Excerpt :

Future research on carbon partitioning from VFAs, between microalgae and bacteria, would also be necessary to precisely estimate carbon assimilation by microalgae after DF. Indeed, under heterotrophic conditions and in presence of fermentative bacteria, Turon et al. suggested that the microalgae growth was assumed to be only due to acetate uptake [67]. But the bacterial growth was observed during acetate removal.

Show abstract Producing omega-3 polyunsaturated fatty acids: A review of sustainable sources and future trends for the EPA and DHA market 2020, Resources View all citing articles on Scopus View full text Copyright © 2015 Elsevier B.V. All rights reserved.