Screening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N:P ratio on vegetative growth

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a 3-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 x 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N:P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N:P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis.BIOVAMA

From Agricultural Waste to Biofuel: Enzymatic Potential of a Bacterial Isolate Streptomyces fulvissimus CKS7 for Bioethanol Production

Purpose To avoid a negative environmental and economic impact of agricultural wastes, and following the principles of circular economy, the reuse of agricultural wastes is necessary. For this purpose, isolation of novel microorganisms with potential biotechnological application is recommended. The current researches in bioethanol production are aimed to reduce the production costs using low-cost substrates and in-house produced enzymes by novel isolated microorganisms. In line with this, in this study valorization of these agricultural by-products by novel isolate S. fulvissimus CKS7 to biotechnological value added products was done. Methods Standard microbiological methods were used for the isolation and characterization of strain. Enzymes activities were determinated using DNS method while, the ethanol concentration was determined based on the density of the alcohol distillate at 20 degrees C. Results The maximal enzymatic activities for amylase, cellulases (carboxymethyl cellulase and Avicelase), pectinase and xylanase were achieved using rye bran as a waste substrate for CKS7 growth. Obtained crude bacterial enzymes were used for enzymatic hydrolysis of lignocellulosic materials including horsetail waste, yellow gentian waste, corn stover, cotton material and corona pre-treated cotton material. The maximum yield of reducing sugars was obtained on horsetail waste and corona pre-treated cotton material. Waste brewer's yeast Saccharomyces cerevisiae was successfully used for the production of bioethanol using horsetail waste hydrolysate and corona pre-treated cotton material hydrolysate. Conclusion The obtained results showed that bacterial strain CKS7 has a significant, still unexplored enzymatic potential that could be used to achieve a cleaner, environmental friendly and economically acceptable biofuel production. [GRAPHICS]

Microalgal Biomass of Industrial Interest: Methods of Characterization

International audienceMicroalgae represent a new source of biomass for many applications. The advantage of microalgae over higher plants is their high productivities. The photoautotrophic microalgae include all photosynthetic microorganisms, i.e. Cyanobacteria (prokaryotes) or microalgae (eukaryotes). These microorganisms are characterized by a large biodiversity and chimiodiversity. Then, the analysis of microalgal and cyanobacterial biomass often needs specific adaptations of the classical protocols for extraction as well as for quantification of their contents. This chapter reviewed the main analytical methods used for the analysis of microalgae biomass and its main vaporizable compounds: proteins, polysaccharides, lipids, pigments and secondary metabolites