Abstract

Microalgae provides an alternative for the valorization of industrial by-products, in which the nutritional content varies substantially and directly affects microalgae system performance. Herein, the heterotrophic cultivation of Chlorella sorokiniana was systematically studied, allowing us to detect a nutritional deficiency other than the carbon source through assessing the oxygen transfer rate for glucose or acetate fermentation. Consequently, a mathematical model of the iron co-limiting effect on heterotrophic microalgae was developed by exploring its ability to regulate the specific growth rate and yield. For instance, higher values of the specific growth rate (0.17 h−1) compared with those reported for the heterotrophic culture of Chlorella were obtained due to iron supplementation. Therefore, anaerobic sludge from an industrial wastewater treatment plant (a baker’s yeast company) was pretreated to obtain an extract as a media supplement for C. sorokiniana. According to the proposed model, the sludge extract allowed us to supplement iron values close to the growth activation concentration (KFe ~12 mg L−1). Therefore, a fed-batch strategy was evaluated on nitrogen-deprived cultures supplemented with the sludge extract to promote biomass formation and fatty acid synthesis. Our findings reveal that nitrogen and iron in sludge extract can supplement heterotrophic cultures of Chlorella and provide an alternative for the valorization of industrial anaerobic sludge.

Highlights

  • During the past decades, industrialization has led to large volumes of generated industrial wastewater and high-organic content waste worldwide [1]

  • We evaluated the impact of iron on the heterotrophic cultivation of C. sorokiniana and the use of anaerobic sludge extract from the industry as an iron source

  • This latter was reached for glucose treatment (E2, 10 g L−1 ) after 25 h, According to the oxygen transfer rate (OTR) course, the E3 and E4 treatments showed the highest biological activity at the beginning of cultivation, directly related to carbon source preference for acetate compared with glucose when both are present [29,30]

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Summary

Introduction

Industrialization has led to large volumes of generated industrial wastewater and high-organic content waste worldwide [1]. Despite advances in wastewater treatment strategies, the final disposal of the sludge generated during treatment remains a critical problem. Anaerobic sludge is produced in lower quantities than aerobically produced sludge, both are commonly managed and disposed of in sanitary landfills or incinerated [2,3]. With these procedures, the contamination and supersaturation of land and water bodies have caused adverse environmental effects [2,3]. A promising alternative includes sludge valorization using microalgae biorefinement processes, which could help to recover or reuse waste and industrial by-products and achieve sustainable biomass production of microalgae for diverse purposes

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