A circular approach for the efficient recovery of astaxanthin from Haematococcus pluvialis biomass harvested by flocculation and water reusability.

Flocculation has been proved an efficient method for microalgal biomass harvesting, but some coagulant agents may have adverse effects on microalgae growth, making the reuse of the medium unfeasible. In this study, Haematococcus pluvialis was harvested by different flocculants, and the feasibility of the reuse of the culture medium was evaluated. Results suggested that both inorganics, polyaluminum chloride (PA) and ferric chloride (FC), and organics, extracted from Moringa oleifera seed (MSE) and chitosan (CH) resulted in efficient flocculation - flocculation efficiency above 99 %. However, using PA and FC had adverse effects on the astaxanthin recovery from haematocysts - losses of 58.6 and 73.5 %, respectively. Bioflocculants in the reused medium also had higher growth performance than inorganic ones. Furthermore, bioflocculants in reused medium increase the contents of ß-carotene, astaxanthin, and linolenic acid. This investigation demonstrated that using MSE and CHI for harvesting H. pluvialis enables the water reusability from a flocculated medium.

Usage of Moringa oleifera residual seeds promotes efficient flocculation of Tetradesmus dimorphus biomass.

Bio-flocculation is a sustainable low-cost harvesting technique for microalgae biomass production; however, it is generally less efficient than chemical flocculants. This study aims to investigate the efficiency of Moringa oleifera seeds as a bio-flocculant for harvesting Tetradesmus dimorphus biomass. Four extracts from integral and residual (seeds without lipids) biomass of M. oleifera seeds using salt or aqueous solutions were used at four concentrations (100, 200, 300, and 400 ppm). Flocculation efficiency (FE) increased as the pH decreased. The addition of the extracts reduced the pH of the cultures, dispensing pH adjustment after dosing the flocculating agent. Salt extracts exhibited higher flocculation efficiency than aqueous extracts. The highest flocculation efficiency (~ 98%) was obtained using a salt extract of residual biomass of seeds in any concentration varying from 100 to 400 ppm. The predicted values obtained from a data modeling using response surface methodology approached the real values (r 2 = 0.9382), resulting in an adequate optimization of the flocculant concentration of ~ 335 ppm and pH 5.6 for a predicted FE of ~ 106%. The findings of the present study confirmed that the salt extract from residual biomass of M. oleifera seeds is an effective bio-flocculant for T. dimorphus biomass harvesting.

Perspectives on the production, structural characteristics and potential applications of bioplastics derived from polyhydroxyalkanoates.

Since the last two decades, the use of synthetic materials has increased and become more frequent in this capitalist system. Polymers used as raw materials are usually disposed very rapidly and considered serious damages when they return to the environment. Because of this behaviour, there was an increasing in the global awareness by minimizing the waste generated, in addition to the scientific community concern for technological alternatives to solve this problem. Alternatively, biodegradable polymers are attracting special interest due to their inherent properties, which are similar to the ones of the conventional plastics. Bioplastics covers plastics made from renewable resources, including plastics that biodegrade under controlled conditions at the end of their use phase. Polyhydroxyalkanoates (PHAs) are polyesters composed of hydroxy acids, synthesized by a variety of microorganisms as intracellular carbon and energy storage. These environmentally friendly biopolymers have excellent potential in domestic, agricultural, industrial and medical field, however their production on a large scale is still limited. This review considered the most recent scientific publications on the production of bioplastics based on PHAs, their structural characteristics and the exploitation of different renewable sources of raw materials. In addition, there were also considered the main biotechnological applications of these biopolymers.

Selection of a protein solubilization method suitable for phytopathogenic bacteria: a proteomics approach.

BACKGROUND: Finding the best extraction method of proteins from lysed cells is the key step for detection and identification in all proteomics applications. These are important to complement the knowledge about the mechanisms of interaction between plants and phytopathogens causing major economic losses. To develop an optimized extraction protocol, strains of Acidovorax citrulli, Pectobacterium carotovorum subsp. carotovorum and Ralstonia solanacearum were used as representative cells in the study of phytopathogenic bacteria. This study aims to compare four different protein extraction methods, including: Trizol, Phenol, Centrifugation and Lysis in order to determine which are more suitable for proteomic studies using as parameters the quantity and quality of extracted proteins observed in two-dimensional gels. RESULTS: The bacteria studied showed different results among the tested methods. The Lysis method was more efficient for P. carotovorum subsp. carotovorum and R. solanacearum phytobacteria, as well as simple and fast, while for A. citrulli, the Centrifugation method was the best. This evaluation is based on results obtained in polyacrylamide gels that presented a greater abundance of spots and clearer and more consistent strips as detected by two-dimensional gels. CONCLUSIONS: These results attest to the adequacy of these proteins extraction methods for proteomic studies.