Divergence in three newly identified Arthrospira species from Mexico.

Arthrospira (Spirulina) is a microalgae that has a unique set of biological characteristics which are very useful for a broad range of applications. Based on its worldwide requirements, this investigation was conducted to collect, isolate and identify the local Arthrospira strains in the central and western part of Mexico. We have successfully collected, isolated and identified (morphologically as well as molecularly) three Arthrospira strains from different regions in Mexico. Morphological studies were conducted by analyzing the size and shape of the helix, the spiral pattern, cell length and width with the help of light microscopy and for molecular analysis, the 16S rRNA and internally transcribed spacer (ITS, 16S-23 rRNA) gene partial sequence were used followed by phylogenetic analysis. The three species were completely different in their filament size and width whereas their ITS sequences were the same in size and more than 87 % similar in nucleotide sequence. The resulted morphological and phylogenetic analysis concluded that the three stains were identified as Arthrospira platensis. Inspite of their morphological variations and differences they were grouped genetically into one cluster along with the A. platensis of reported strains of Gene Bank database (NCBI). One of the isolated strains NPS-0, is probably the biggest Arthrospira strains ever reported and can be suitable for industrial scale biomass and protein production.

Microalgae as a potential natural source for the green synthesis of nanoparticles.

The increasing global population is driving the development of alternative sources of food and energy, as well as better or new alternatives for health and environmental care, which represent key challenges in the field of biotechnology. Microalgae represent a very important source material to produce several high-value-added bioproducts. Due to the rapid changes in the modern world, there is a need to build new materials for use, including those in the nanometer size, although these developments may be chronological but often do not occur at a time. In the last few years, a new frontier has opened up at the interface of biotechnology and nanotechnology. This new frontier could help microalgae-based nanomaterials to possess new functions and abilities. Processes for the green synthesis of nanomaterials are being investigated, and the availability of biological resources such as microalgae is continuously being examined. The present review provides a concise overview of the recent advances in the synthesis, characterization, and applications of nanoparticles formed using a wide range of microalgae-based biosynthesis processes. Highlighting their innovative and sustainable potential in current research, our study contributes towards the in-depth understanding and provides latest updates on the alternatives offered by microalgae in the synthesis of nanomaterials.

Phycocyanin content and nutritional profile of Arthrospira platensis from Mexico: efficient extraction process and stability evaluation of phycocyanin.

Phycocyanin is a blue natural food colorant with multiple health benefits. Here we propose an efficient phycocyanin extraction method from Arthrospira platensis from Mexico. Three extraction methods were applied to optimize the extraction process, using water and buffer as solvents, with three pH values at two agitation times. The highest phycocyanin, 54.65 mg/g, was extracted from dry biomass with water as a solvent using an ultrasonication bar. The optimum condition of extraction was determined to be 1:50 biomass/solvent ratio for dry biomass, with the freeze/thaw method for 20 min repeated twice, and then agitated at 120 rpm for 24 h. The phycocyanin content was 48.88 mg/g biomass, with a purity of 0.47. For scalable phycocyanin productivity, the sonication method is recommended as there is no statistical difference. The phycocyanin stability was best at - 20 °C storage temperature at pH 7 for 35 days. Partial purification with ammonium sulfate was found to be suitable as a fractional precipitation method, first at 0-20% and then 20-65%, to get purity nearly 1. Total protein was found to be 55.52%, and total amino acids after phycocyanin extraction was 33%. The maximum phycocyanin yield using water as a solvent was the most interesting result regardless of the method used for extraction.

Molecular cloning, characterization and regulation of two different NADH-glutamate synthase cDNAs in bean nodules.

NADH-dependent glutamate synthase (NADH-GOGAT) is a key enzyme in primary ammonia assimilation in Phaseolus vulgaris nodules. Two different types of cDNA clones of PvNADH-GOGAT were isolated from the nodule cDNA libraries. The full-length cDNA clones of PvNADH-GOGAT-I (7.4 kb) and PvNADH-GOGAT-II (7.0 kb), which displayed an 83% homology between them, were isolated using cDNA library screening, 'cDNA library walking' and RT-PCR amplification. Southern analysis employing specific 5' cDNA probes derived from PvNADH-GOGAT-I and PvNADH-GOGAT-II indicated the existence of a single copy of each gene in the bean genome. Both these proteins contain approximately 100 amino acid sequences theoretically addressing each isoenzyme to different subcellular compartments. RT-PCR analysis indicated that PvNADH-GOGAT-II expression is higher than PvNADH-GOGAT-I during nodule development. Expression analysis by RT-PCR also revealed that both of these genes are differentially regulated by sucrose. On the other hand, the expression of PvNADH-GOGAT-I, but not PvNADH-GOGAT-II, was inhibited with nitrogen compounds. In situ hybridization and promoter expression analyses demonstrated that the NADH-GOGAT-I and -II genes are differentially expressed in bean root and nodule tissues. In silico analyses of the NADH-GOGAT promoters revealed the presence of potential cis elements in them that could mediate differential tissue-specific, and sugar and amino acid responsive expression of these genes.

Evidence for sugar signalling in the regulation of asparagine synthetase gene expressed in Phaseolus vulgaris roots and nodules.

A cDNA clone, designated as PvNAS2, encoding asparagine amidotransferase (asparagine synthetase) was isolated from nodule tissue of common bean (Phaseolus vulgaris cv. Negro Jamapa). Southern blot analysis indicated that asparagine synthetase in bean is encoded by a small gene family. Northern analysis of RNAs from various plant organs demonstrated that PvNAS2 is highly expressed in roots, followed by nodules in which it is mainly induced during the early days of nitrogen fixation. Investigations with the PvNAS2 promoter gusA fusion revealed that the expression of PvNAS2 in roots is confined to vascular bundles and meristematic tissues, while in root nodules its expression is solely localized to vascular traces and outer cortical cells encompassing the central nitrogen-fixing zone, but never detected in either infected or non-infected cells located in the central region of the nodule. PvNAS2 is down-regulated when carbon availability is reduced in nodules, and the addition of sugars to the plants, mainly glucose, boosted its induction, leading to the increased asparagine production. In contrast to PvNAS2 expression and the concomitant asparagine synthesis, glucose supplement resulted in the reduction of ureide content in nodules. Studies with glucose analogues as well as hexokinase inhibitors suggested a role for hexokinase in the sugar-sensing mechanism that regulates PvNAS2 expression in roots. In light of the above results, it is proposed that, in bean, low carbon availability in nodules prompts the down-regulation of the asparagine synthetase enzyme and concomitantly asparagine production. Thereby a favourable environment is created for the efficient transfer of the amido group of glutamine for the synthesis of purines, and then ureide generation.

Chemical stability of astaxanthin integrated into a food matrix: Effects of food processing and methods for preservation.

Astaxanthin is a carotenoid pigment found in numerous organisms ranging from bacteria to algae, yeasts, plants, crustaceans and fish such as salmon. Technological importance of this pigment emerged from various studies demonstrating that it is a powerful antioxidant, even with higher activity than alpha-tocopherol and other carotenoids. It has been included in various pharmaceutical products because of several beneficial properties. By its nature, astaxanthin is susceptible to degradation and can undergo chemical changes during food processing. Therefore, different studies have focused on improving the stability of the carotenoid under conditions such as high temperatures, pressures and mechanical force, among others. In this review, common processes involved in food processing and their effect on the stability of astaxanthin, integrated into a food matrix are discussed. Moreover, preservation techniques such as microencapsulation, inclusion in emulsions, suspensions, liposomes, etc., that are being employed to maintain stability of the product are also reviewed.