Ciencias Exactas y Ciencias de la Salud

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Reduction of chemical oxygen demand of nejayote and production of potentially bioactive polysaccharides after fermentation with alkaline microalgae-cyanobacteria consortium
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2022-06-14) Del valle Real, Marinat; Gutiérrez Uribe, Janet Alejandra; 274602; Gutiérrez Uribe, Janet Alejandra; puemcuervo; Luna Vital, Diego Armando; School of Engineering and Sciences; Campus Puebla; Franco Morgado, Mariana
Alkaline wastewater from maize lime-cooking, commonly known in Mexico as nejayote, contains a significant amount of soluble solids and a chemical oxygen demand (COD) higher than 11,400 ± 141 mg O2 L-1. After a sedimentation process, supernatants of this effluent were fermented for 15 days with an alkaliphilic microalgae-cyanobacteria consortium (AMC). The project was divided in two parts: a laboratory scale and pilot scale. At laboratory scale, flasks of 1000 mL were used to growth AMC in mineral salt medium (MSM) used as control (M) and inoculum. Nejayote was obtained from a local tortilla bakery and sterilized (NE and N) to compare the effect of endogenous microorganisms besides AMC in the production of byproducts after their fermentation. In addition, nejayote was used as a blank without AMC (NB). For pilot scale a 100 L High-Rate Algal Pond (HRAP) photobioreactor was used where AMC was grown with MSM (MSM-HRAP), nejayote was used to grow AMC (N-HRAP) and nejayote was used as a blank (NB-HRAP). At laboratory scale M produced higher AMC biomass, reaching 228%, than N, NE, or NB, which reached 35%, 26% and 28%, respectively. After 15 days, a pH reduction was observed in N fermentation going from 9.5 to 8.76 in contrast to the increase from 9 to 10 in M. NE showed the best COD removal, reaching more than 50% efficiency after 12 days of fermentation. For pilot scale NB-HRAP produced the highest biomass concentration reaching 300% after 7 days. None of the fermentations showed a significant COD removal since organic matter such as carbohydrates increased. Significant differences were observed in the polysaccharides and protein content of the biomass recovered from control (M) compared with the fermentation process using nejayote as a culture media. Particularly, NB had the highest intracellular protein (ICP) content with a 24% ± 2% DW, followed by NE with 19% ± 0.4% and N with 16% ± 1%. Moreover, an increase of extracellular polysaccharides (EPS) and proteins was observed during the fermentations reaching a maximum concentration of 16217 土 1910 μg mL-1 and 7475 土 2152 μg mL-1 at day 6. Further analysis of the amino acid profile, functionality, and stability of this potential single cell protein (SCP) production process should be considered to promote the use of this strategy to reduce COD and generate added value products.
Characterization of the effect of UV-A light and agitation on the exopolysaccharide production of Chlorella vulgaris and Porphyridium cruentum
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2022-05) Garza Rodríguez, Zaida Berenice; GARZA RODRIGUEZ, ZAIDA BERENICE; 838147; Benavides Lozano, Jorge Alejandro; emipsanchez; Jacobo Velázquez, Daniel Alberto; Santacruz López, Yolanda Arlette; School of Engineering and Sciences; Campus Monterrey; Hernández Pérez, Jesús
Microalgae species are photosynthetic microorganisms that are a sustainable source of bioproducts due to their ability to reduce anthropogenic carbon dioxide in the atmosphere. The number of studies focused on their biologically active molecules, such as lipids, proteins, polysaccharides, and pigments, has been increasing in the last years due to their promising application as valuable products. In this context, the exopolysaccharides (EPS) from microalgal sources stand out as high-value molecules for their potential applications in the nutraceutical and pharmaceutical industries. However, studies aimed to find strategies and optimal conditions to promote the biosynthesis of EPS are still required to make these molecules economically feasible. The effect of ultraviolet light A (UV-A) is studied on biomass and EPS productivity of the red microalgae Porphyridium cruentum and the green microalgae Chlorella vulgaris testing three levels: L0, L1 and L2. Likewise, the effect of the agitation factor on cell growth and EPS productivity are analyzed for the two microalgae species testing two levels: A0 and A1. After recovering the EPS using centrifugation and diafiltration, their potential antioxidant activity was tested using the 2,2-Diphenyl-1-prykylhydrazyl (DPPH) radical scavenging assay. The UV-A light (315-400 nm), along with photosynthetic active radiation (PAR) increased EPS productivity in both C. vulgaris and P. cruentum to 1.21-fold and 2.43-fold, respectively, compared to light control conditions (PAR at 35.6 µmol m⁻² s⁻ ¹). The highest P. cruentum EPS productivity was 8.67 mg/g DW biomass at the highest tested UV-A level and lowest agitation(L2A0), and the highest biomass concentration was 8.57 g/L at the highest agitation (A1) due to a possible improvement in nutrient distribution. For C. vulgaris, the highest productivity was 1380 mg/g DW biomass at intermediate UV-A light level (L1). The highest biomass concentration of C. vulgaris was 0.34 g/L at the highest UV-A level (L2), treatment that conversely displayed the lowest EPS productivity (73.08 mg/g DW biomass). The study of antioxidant activity revealed that EPS show DPPH radical scavenging activity. The mean highest radical scavenging effect (%) of P. cruentum and C. vulgaris EPS was 56.48 ± 4.46 and 46.31 ± 3.2 at 4 mg/mL and 2 mg/mL, respectively. This work contributes to the characterization of abiotic factors that could potentially influence the production of high-value EPS molecules that display bioactivity of interest for health applications.

Ciencias Exactas y Ciencias de la Salud

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