Yeast assisted algal flocculation for enhancing nutraceutical potential of Chlorella pyrenoidosa

Investigating cultivation strategies for enhancing protein content in Auxenochlorella pyrenoidosa FACHB-5

This study investigated the influence of yeast extract addition, carbon source, and photoperiod on the growth dynamics of Auxenochlorella pyrenoidosa FACHB-5. Employing response surface methodology, the culture strategy was optimized, resulting in the following optimal conditions: yeast extract addition at 0.75 g L-1, glucose concentration of 0.83 g L-1, and a photoperiod set at Light: Dark = 18 h: 6 h. Under these conditions, the biomass reached 1.76 g L-1 with a protein content of 750.00 g L-1, containing 40 % of essential amino acids, representing a 1.52-fold increase. Proteomic analysis revealed that the targeted cultivation strategy up-regulated genes involved in microalgal protein synthesis. The combined effect of yeast extract and glucose enhanced both the glutamine synthetase-glutamate synthetase mechanism and the free amino acid content.

Technologies for harvesting the microalgae for industrial applications: Current trends and perspectives

Microalgae are emerging as a promising source for augmenting the supply of essential products to meet global demands in an environmentally sustainable manner. Despite the potential benefits of microalgae in industry, the high energy consumption for harvesting remains a significant obstacle. This review offers a comprehensive overview of microalgae harvesting technologies and their industrial applications, with particular emphasis on the latest advances in flocculation techniques. These cutting-edge methods have been applied to biodiesel production, food and nutraceutical processing, and wastewater treatment. Large-scale harvesting is still severely impeded by the high cost despite progress has been made in laboratory studies. In the future, cost-effective microalgal harvesting will rely on efficient resource utilization, including the use of waste materials and the reuse of media and flocculants. Additionally, precise regulation of biological metabolism will be necessary to overcome algal species-related limitations through the development of extracellular polymeric substance-induced flocculation technology.

Development of yeast and microalgae consortium biofilm growth system for biofuel production

Background

The current study aimed to develop a laboratory-scale biofilm photobioreactor system for biofuel production.

Scope & Approach

During the investigation, Jute was discovered to be the best, cheap, hairy, open-pored supporting material for biofilm formation. Microalgae & yeast consortium was used in this study for biofilm formation.

Conclusion

The study identified microalgae and yeast consortium as a promising choice and ideal partners for biofilm formation with the highest biomass yield (47.63 ± 0.93 g/m2), biomass productivity (4.39 ± 0.29 to 7.77 ± 0.05 g/m2/day) and lipid content (36%) over 28 days cultivation period, resulting in a more sustainable and environmentally benign fuel that could become a reality in the near future.

A phyco-nanobionics biohybrid system for increased carotenoid accumulation in C. sorokiniana UUIND6

Recent advancements in "phyco-nanobionics" have sparked considerable interest in the ability of microalgae to synthesize high-value natural bioactive compounds such as carotenoid pigments, which have been highlighted as an emergent and vital bioactive compound from both industrial and scientific perspectives. Such bioactive compounds are often synthesized by either altering the biogenetic processes existing in living microorganisms or using synthetic techniques derived from petroleum-based chemical sources. A bio-hybrid light-driven cell factory system was established herein by using harmful macroalgal bloom extract (HMBE) and efficient light-harvesting silver nanoparticles (AgNPs) to synthesize HMBE-AgNPs and integrating the synthesized HMBE-AgNPs in various concentrations (1, 2.5, 5 and 10 ppm) into the microalgae C. sorokiniana UUIND6 to improve the overall solar-to-chemical conversion efficiency in carotenoid pigment synthesis in microalgae. The current study findings found high biocompatibility of 5 ppm HMBE-AgNP concentration that can serve as a built-in photo-sensitizer and significantly improve ROS levels in microalgae (6.75 ± 0.25 μmol H2O2 g-1), thus elevating total photosynthesis resulting in a two-fold increase in carotenoids (457.5 ± 2.5 μg mL-1) over the native microalgae without compromising biomass yield. NMR spectroscopy was additionally applied to acquire a better understanding of pure carotenoids derived from microalgae, which indicated similar peaks in both spectra when compared to β-carotene. Thus, this well-planned bio-hybrid system offers a potential option for the cost-effective and long-term supply of these natural carotenoid bio-products.

Effect of environmental stresses during fermentation on brewing yeast and exploration on the novel flocculation-associated function of RIM15 gene

Flocculation of brewer's yeast is an environment-friendly and cost-effective way to separate yeast cells from fermentation broth for subsequent production. Diverse genetic background and complex fermentation environment cause difficulty to explore flocculation mechanism and regulate yeast flocculation. In this study, comparative transcriptome analysis was carried out between an industrial brewing yeast and its flocculation-enhanced mutant strain, unveiling the differentially-expressed genes were enriched in response to stresses. The expression level of Lg-FLO1 was the highest among all FLO genes. Environmental stresses of fermentation were simulated to stimulated yeast cells and it was found that nitrogen and amino acid starvation promoted the process of flocculation. It is the first time to reveal the nutrient-responsive gene RIM15 has a novel genetic function regulating flocculation. The study provides novel direction and strategies to manage yeast flocculation and achieve effective cell utilization in fermentation.

Recent advances in CO2 fixation by microalgae and its potential contribution to carbon neutrality

Many countries and regions have set their schedules to achieve the carbon neutrality between 2030 and 2070. Microalgae are capable of efficiently fixing CO₂ and simultaneously producing biomass for multiple applications, which is considered one of the most promising pathways for carbon capture and utilization. This work reviews the current research on microalgae CO₂ fixation technologies and the challenges faced by the related industries and government agencies. The technoeconomic analysis indicates that cultivation is the major cost factor. Use of waste resources such as wastewater and flue gas can significantly reduce the costs and carbon footprints. The life cycle assessment has identified fossil-based electricity use as the major contributor to the global warming potential of microalgae-based CO₂ fixation approach. Substantial efforts and investments are needed to identify and bridge the gaps among the microalgae strain development, cultivation conditions and systems, and use of renewable resources and energy.

Small peptide glutathione-induced bioflocculation for enhancing the food application potential of Chlorella pyrenoidosa

Existing flocculants are used to enhance the harvesting efficiency of microalgae; however, harvesting biomass containing residues is unsuitable for food applications. In this study, a small peptide-induced bioflocculation technique was developed for harvesting microalgae, and the biomass was free of impurities. After seven days of cultivation with glutathione, 72 % flocculation efficiency of Chlorella pyrenoidosa was achieved after settling for 1 h. The nutrient composition of flocs depicted a higher protein (68.94 mg/L) and lipid (48.97 mg/L) content than those of the control (65.91 and 41.44 mg/L). The amino acid profiles of flocs showed the presence of more essential amino acids than in untreated cells. More omega polyunsaturated fatty acids, such as ω-3 and ω-9, accumulate in flocs. Extracellular polymeric substances, which induced bioflocculation, appeared markedly in flocs (150.02 mg/L) compared to the control (32.30 mg/L). This study provides novel insights into the residue-free algal harvesting method and obtained nutrition-enriched biomass.