Jin Hyuk Shin

The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products

Microalgae have recently attracted considerable interest worldwide, due to their extensive application potential in the renewable energy, biopharmaceutical, and nutraceutical industries. Microalgae are renewable, sustainable, and economical sources of biofuels, bioactive medicinal products, and food ingredients. Several microalgae species have been investigated for their potential as value-added products with remarkable pharmacological and biological qualities. As biofuels, they are a perfect substitute to liquid fossil fuels with respect to cost, renewability, and environmental concerns. Microalgae have a significant ability to convert atmospheric CO2 to useful products such as carbohydrates, lipids, and other bioactive metabolites. Although microalgae are feasible sources for bioenergy and biopharmaceuticals in general, some limitations and challenges remain, which must be overcome to upgrade the technology from pilot-phase to industrial level. The most challenging and crucial issues are enhancing microalgae growth rate and product synthesis, dewatering algae culture for biomass production, pretreating biomass, and optimizing the fermentation process in case of algal bioethanol production. The present review describes the advantages of microalgae for the production of biofuels and various bioactive compounds and discusses culturing parameters.

Enhancing the Feasibility of Microcystis aeruginosa as a Feedstock for Bioethanol Production under the Influence of Various Factors

Microcystis aeruginosa, a freshwater microalga, is capable of producing and accumulating different types of sugars in its biomass which make it a good feedstock for bioethanol production. Present study aims to investigate the effect of different factors increasing growth rate and carbohydrates productivity of M. aeruginosa. MF media (modified BG11 media) and additional ingredients such as aminolevulinic acid (2 mM), lysine (2.28 mM), alanine (1 mM), and Naphthalene acetic acid (1 mM) as cytokine promoted M. aeruginosa growth and sugar contents. Salmonella showed growth-assisting effect on M. aeruginosa. Enhanced growth rate and carbohydrates contents were observed in M. aeruginosa culture grown at 25°C under red LED light of 90 μmolm−2s−1 intensity. More greenish and carbohydrates rich M. aeruginosa biomass was prepared (final OD660 nm = 2.21 and sugar contents 10.39 mM/mL) as compared to control (maximum OD660 nm = 1.4 and sugar contents 3 mM/mL). The final algae biomass was converted to algae juice through a specific pretreatment method. The resulted algae Juice was used as a substrate in fermentation process. Highest yield of bioethanol (50 mM/mL) was detected when Brettanomyces custersainus, Saccharomyces cerevisiae, and Pichia stipitis were used in combinations for fermentation process as compared to their individual fermentation. The results indicated the influence of different factors on the growth rate and carbohydrates productivity of M. aeruginosa and its feasibility as a feedstock for fermentative ethanol production.

HPLC fractionation and pharmacological assessment of green tea seed saponins for antimicrobial, anti-angiogenic and hemolytic activities

Herbal medicinal products have proven to be safe, economical and effective alternatives to synthetic chemical pharmaceuticals. The green tea plant (Camellia sinensis) is of profound medicinal value due to the presence of potent bioactive constituents. The purpose of the present work is to investigate saponins from green tea seeds for potential use as anti-angiogenic, antimicrobial, and hemolytic agents. Green tea seed saponins were separated into six fractions by reverse phase HPLC. The presence of three aglycone chains in the saponins of each fraction was confirmed by acid hydrolysis. Anti-angiogenic activity was evaluated using saponin fractions at concentrations in the range of 2.5 ~ 25 μg/mL. Antimicrobial activity was evaluated by thin-layer chromatography (TLC) using E. coli; S. mutans, a zoonotic Salmonella species and the fungal strain, A. niger. Saponin fractions were more potent against E. coli (gram negative bacteria) than against S. mutans (gram positive bacteria) and strongly inhibited six strains of zoonotic Salmonella. Green tea saponins also showed potent anti-angiogenic effects. All saponin fractions exhibited hemolytic activity. Our results confirm that green tea saponins have antimicrobial, anti-angiogenic, and hemolytic activities; indicating their potential as natural pharmaceutical products.

In vivo and In vitro Antimicrobial Effects of Natural Antibiotics Present in Crude Extracts of Various Medicinal Plants

Bacteria are among the most common causes of severe diseases in both plants and animals. Salmonella spp. has deleterious effects and is the cause of various transmittable diseases. Because of strains resistivity, side effects and high prices of synthetic antibiotics, it has become essential to explore safe and economical natural sources of antibiotics. In this study, growth inhibitory effects of natural antibiotics present in crude extracts of Galla rhois, Thujae semen, Paeonia japonica, and Armeniacae semen were investigated both in vivo and iv vitro. Ethanol extracts of the above-mentioned plants were prepared and tested against seven serovars of Salmonella and Escherichia coli by disc diffusion method. In addition, the antibacterial effects of the plant extracts were determined in vivo using ducks as model animals. Reverse transcription-polymerase chain reaction was performed using blood and fecal samples of control, infected, and treated groups of the ducks to determine the gene expression levels of the bacteria. Our results confirmed that the Galla rhois ethanol extract had the highest antibacterial activity among the plant extracts when they were used individually. However, the Galla rhois, Thujae semen, and P. japonica ethanol extracts showed stronger antibacterial effects against all the bacterial species used when the extracts were combined at a ratio of 3:3:2, respectively.