Growth Performance, Biochemical Composition and Nutrient Recovery Ability of Twelve Microalgae Consortia Isolated from Various Local Organic Wastes Grown on Nano-Filtered Pig Slurry

Min Su,Barbara Scaglia,Alessia Bani,Giuliana D’Imporzano,Marta Dell’Orto,Fabrizio Adani

doi:10.3390/molecules27020422

Abstract

This paper demonstrated the growth ability of twelve algae-microbial consortia (AC) isolated from organic wastes when a pig slurry-derived wastewater (NFP) was used as growth substrate in autotrophic cultivation. Nutrient recovery, biochemical composition, fatty acid and amino acid profiles of algae consortia were evaluated and compared. Three algae-microbial consortia, i.e., a Chlorella-dominated consortium (AC_1), a Tetradesmus and Synechocystis co-dominated consortium (AC_10), and a Chlorella and Tetradesmus co-dominated consortium (AC_12) were found to have the best growth rates (µ of 0.55 ± 0.04, 0.52 ± 0.06, and 0.58 ± 0.03 d−1, respectively), which made them good candidates for further applications. The ACs showed high carbohydrates and lipid contents but low contents of both proteins and essential amino acids, probably because of the low N concentration of NFP. AC_1 and AC_12 showed optimal ω6:ω3 ratios of 3.1 and 3.6, which make them interesting from a nutritional point of view.

Highlights

Nano-Filtered Permeate (NFP) appeared suitable for microalgae growth (Table 1) because it contained 136 ± 0 mg L−1 of Total nitrogen (TN), 97% of which was in the ammonium
Microalgae consortia isolated from high ammonia-content wastes, such as the ones used in this work, have the potential to cope better with high ammonia concentrations
41.2 ± 10.6%, 37 ± 8.6% and 21.9 ± 6.6% of the total lipid content (Figure 1c). These figures are in line with data reported for Chlorella sp., i.e., SFAs of 38.1 ± 12.5%, polyunsaturated fatty acids (PUFAs) of 39 ± 12.9% and monounsaturated fatty acids (MUFAs) of 22.8 ± 6.3% of total lipids (n = 12), respectively [17,47,63,64], as well as in agreement with the results reported for Tetradesmus sp., SFAs 45.2 ± 3.3%, PUFAs

Summary

Introduction

Microalgae cultivation is considered to be an efficient tool in the framework of a circular economy, combining wastewater treatment and the production of valuable biomass for various purposes [1]. The chemical compositions of several kinds of wastewater are quite similar to the culture media usually adopted for microalgae growth; the possibility to recover inorganic nutrients, water and CO2 from wastewaters and organic wastes provides an environmentally friendly and cheap method for algae production [2]. Inorganic nitrogen (N) and phosphorus (P) uptake by microalgae can be used as an efficient bioremediation tool for wastewater treatment, transforming these nutrients into energy-rich biomass, which can be further processed to make biofuels or other valuable products such as biofertilizers, bioplastics and so forth [4]

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Conclusion