Main Variables Affecting a Chemical-Enzymatic Method to Obtain Protein and Amino Acids from Resistant Microalgae

he development of microalgae uses requires further investigation in cell disruption alternatives to reduce the costs associated to this processing stage. This study aimed to evaluate the main variables affecting an extraction method to obtain protein and amino acids from microalgae. The method was based on a sequential alkaline-enzymatic process, with separate extractions and noncontrolled pH, and was applied to fresh biomass of a resistant species. The processed microalgae were composed of a consortium with Nannochloropsis sp. as predominant species. After the optimization of the pH of the alkaline reaction, the effect of the time of the alkaline reaction (30-120min), the time (30-120min) and temperature (40-60 degrees C) of the enzymatic reaction, and the biomass concentration (50-150mgml(-1)), on the extraction yields of protein and free amino nitrogen (FAN) and on the final concentration of protein in the extract, was studied using a response surface methodology. Even though all the variables and some interactions among them had a significant effect, the biomass concentration was the most important factor affecting the overall process. The results showed relevant information about the different options in order to maximize not only the response variables individually but also different combinations of them. Assays with optimized values reached maximum yields of 80.3% and 1.07% of protein (% of total protein) and FAN (% of total biomass), respectively, and a protein concentration in the extract of 15.2mgml(-1). The study provided the essential information of an alternative approach to obtain protein and amino acids from fresh biomass of resistant microalgae with a high yield, also opening perspectives for further research in particular aspects

Versatile method to obtain protein- and/or amino acid-enriched extracts from fresh biomass of recalcitrant microalgae without mechanical pretreatment

The aim of the study was to develop a sequential alkaline-enzymatic method to obtain protein- and/or amino acid-enriched extracts from fresh biomass of recalcitrant microalgae without any supplementary pretreatment. The effects of the initial biomass concentration, the use of freeze-dried or fresh biomass, enzyme dosage, processing procedure (two-step and single-step, with and without pH control) and species were studied. The method was evaluated with a consortium of microalgae isolated from a landfill leachate and was tested on other recognized recalcitrant microalgae such as Chlorella vulgaris, Nannochloropsis gaditana and Scenedesmus obliquus. The approach includes alternative pathways, provides high extraction yields of proteinaceous material and produces protein- and/or hydrolyzed peptide-enriched extracts with different amino acid compositions (e.g., a pathway without pH control achieves a yield of 81% of total protein and a concentration of 29 mg mL−1 of proteinaceous material). The versatility in processing procedures and the range of products obtained, along with applicability to different microalgal species, make this method an interesting option for algae biomass treatment. Furthermore, the high yield and simplicity from a technological point of view, gives it a great potential for process development and encourages further research for a wide variety of applications, such as feed, biostimulants, culture media, bulk chemicals, and biogas

Application of a Microalgal Peptide-Enriched Extract as Media Component in E. coli Culture

This study evaluated the feasibility of applying a microalgal peptide-enriched extract, obtained through a sequential alkaline and enzymatic method, as a fundamental media component in Escherichia coli culture. The results demonstrated that the extract is viable as the primary nutrient source for E. coli cultures (wild type), even as a complete substitute for the widely used Luria-Bertani (LB) medium, using an extract dilution of 1:3. Its application in a proportion carbon limiting (dilution 1:7), with glycerol supplementation at the early stationary phase, improved the nutrient use efficiency and controlled the undesirable acetate production. Furthermore, this last strategy applied in an E. coli mutant (M4-Delta iclR) enhanced the production of succinate by 67.3% compared with the M9 medium. The innovative approach proposed in this study opens a wide range of applications and studies related to the production of bio-compounds through diverse microorganisms

Uveal vs. cutaneous melanoma. Origins and causes of the differences.

International audienceMelanoma is a malignant tumour derived from melanocytes (dendritic cells originated from the neural crest and capable to produce melanin synthesis) that could be established on the skin or less frequently on the uvea. The cellular origin from both kind of melanoma seems to be the same but the melanocytes migrates to the epithelia for cutaneous melanoma, while for uveal melanoma, they migrate to mesodermic tissues. Despite the common origin, both melanomas show extreme differences in their metastatic potential, clinical response to treatments, immune response and genetic alterations. We will describe some of those differences in this review