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Bioprospecting of cyanobacteria from Thai karstic caves as potential producers of phenolic compounds with antioxidant capacity
(2026-04-01)
Suphan, Sutthawan
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Kula, Kasinee
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Lomthong, Thanasak
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Sujarit, Kanaporn
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Maneeruttanarungroj, Cherdsak
Cyanobacteria are highly adaptable microorganisms that can survive in extreme environments. Survival of cyanobacteria in assorted habitats has positively impelled them to produce a range of bioactive compounds, which show a variety of beneficial biological activities. The karstic caves are harsh environments with low light and nutrient input and serve as a unique habitat for exploring cyanobacterial biodiversity as producers of natural products of economic and ecological importance. A total of 86 cyanobacterial strains isolated from 23 karstic caves in four regions of Thailand showed photosynthetic pigments correlated with growth performance and exhibited potential for producing phenolic compounds with significant antioxidant capacity. Based on DPPH scavenging efficiency per unit concentration of crude extract, Leptolyngbya sp. LKK14, Nostoc sp. SW02, and Leptolyngbya sp. LP01 exhibited the superior antioxidant potency. The highest contents of total phenolics (42.10 mgGAE/gCE) and flavonoids (395.90 mgQE/gCE) were found in Leptolyngbya sp. LP01 extract. The presence of phenolic compounds correlated with antioxidant activity; Leptolyngbya sp. LP01 showed the highest antioxidant activity, as measured by DPPH, ABTS, and FRAP assays, with respective values of 15.79, 20.87, and 42.69 mgAAE/gCE. Nine phenolic compounds were tentatively identified based on MS/MS fragmentation patterns compared with library data by LC-ESI-QTOF-MS/MS approach, suggesting that the extract of Leptolyngbya sp. LP01 contains valuable biological antioxidants. This study contributes to our current understanding of cyanobacterial biodiversity in poorly studied habitats, particularly in terms of their biotechnological potential as producers of secondary metabolites suitable for application in the food, pharmaceutical, and cosmetic industries.
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Modified natural seawater as growth medium for the halotolerant cyanobacterium Aphanothece halophytica to increase lipid content for biodiesel production
(2025-02-01)
Thongtha, Sitthichai
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Aryusuk, Kornkanok
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Kittiwongwattana, Chokchai
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Incharoensakdi, Aran
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Phunpruch, Saranya
Biodiesel derived from cyanobacterial oils becomes attractive as an efficient renewable energy. The present study aims to optimize growth and lipid production of the halotolerant unicellular cyanobacterium Aphanothece halophytica cultivated in natural seawater. In this study A. halophytica was able to grow in natural seawater when supplemented with low concentration of NaNO<inf>3</inf>, whereas no growth occurred without supplementation. The specific growth rate of 0.230 day-1 and cell concentration of 25.17 x 106 cells mL-1 were achieved in A. halophytica cultivated in natural seawater supplemented with 17.6 mM NaNO<inf>3</inf> and Turk Island salt solution (suitable natural seawater; SNSW) for 14 days. This growth rate was comparable to that of cells grown in normal BG11 plus Turk Island salt solution. The lipid content and fatty acid profiles of A. halophytica varied with changes in NaCl concentrations. The highest lipid content of 50.47 % and lipid productivity of 48.33 mg L-1 day-1 were obtained in cultures supplemented with 1.89 mmol C-atom L-1 glucose and 0.75 M NaCl. The optimal medium pH and cultivation temperature for lipid production was 7.5 and 25-35 °C, respectively. When cultivating A. halophytica in optimized SNSW with various NaCl concentrations, the highest contents of linoleic and linolenic acids, and the lowest contents of palmitic, stearic, and oleic acids were observed with 0.75 M NaCl. In contrast, cultures grown in optimized SNSW with 0.5 M NaCl showed fatty acid methyl ester profiles rich in monounsaturated fatty acids, which are favorable for high-quality biodiesel production.
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Characterization and exploration of biological properties of phycobiliproteins purified from Thai karstic cave cyanobacterium Nostoc sp. SW02
(2023-09-01)
Suphan, Sutthawan
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Limrujiwat, Kittakorn
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Kula, Kasinee
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Maneeruttanarungroj, Cherdsak
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Raksajit, Wuttinun
Phycobiliproteins are colored water-soluble proteins found in cyanobacteria with potential applications in food and pharmaceuticals. Phycobiliproteins extracted from the Thai karstic cave cyanobacterium Nostoc sp. strain SW02 were purified, and their biological properties were characterized. Scale-up cultivation for 12 days revealed that maximum biomass and phycobiliproteins producing yield were 1.53 g/L and 31.92%, respectively. After purification, phycoerythrin was obtained as the principal component of phycobiliproteins, with a purity index up to 2.62, sufficient to be considered food and cosmetic grade. Native and SDS-PAGE analysis displayed that purified phycoerythrin and phycocyanin contained the αβ-subunits in hexamer form. Purified phycobiliproteins had a more stable structure and functionality in pH range 5.0–7.0, were resistant to strong oxidizers, and could withstand temperatures up to 60 °C. They also exhibited DPPH scavenging capabilities comparable to standard ascorbic acid. Pathogenic bacterial inhibition (MIC 250 μg/mL) and anticancer activity against the human HeLa cancer cell line (IC<inf>50</inf> 140 μg/mL) were also observed. With these prospective characteristics, phycobiliproteins obtained from Nostoc sp. SW02 have biotechnological value for biomedical research and also as a natural colorant for food and cosmetic applications.
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Photobiohydrogen Production and Strategies for H2 Yield Improvements in Cyanobacteria
(2023-01-01)
Khetkorn, Wanthanee
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Raksajit, Wuttinun
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Maneeruttanarungroj, Cherdsak
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Lindblad, Peter
Hydrogen gas (H<inf>2</inf>) is one of the potential future sustainable and clean energy carriers that may substitute the use of fossil resources including fuels since it has a high energy content (heating value of 141.65 MJ/kg) when compared to traditional hydrocarbon fuels [1]. Water is a primary product of combustion being a most significant advantage of H<inf>2</inf> being environmentally friendly with the capacity to reduce global greenhouse gas emissions. H<inf>2</inf> is used in various applications. It generates electricity in fuel cells, including applications in transportation, and can be applied as fuel in rocket engines [2]. Moreover, H<inf>2</inf> is an important gas and raw material in many industrial applications. However, the high cost of the H<inf>2</inf> production processes requiring the use of other energy sources is a significant disadvantage. At present, H<inf>2</inf> can be prepared in many conventional ways, such as steam reforming, electrolysis, and biohydrogen production processes. Steam reforming uses high-temperature steam to produce hydrogen gas from fossil resources including natural gas. Electrolysis is an electrolytic process to decompose water molecules into O<inf>2</inf> and H<inf>2</inf>. However, both these two methods are energy-intensive and producing hydrogen from natural gas, which is mostly methane (CH<inf>4</inf>) and in steam reforming generates CO<inf>2</inf> and pollutants as by-products. On the other hand, biological hydrogen production is more environmentally sustainable and less energy intensive than thermochemical and electrochemical processes [3], but most concepts are not yet developed to production scale.
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Enhanced dark fermentative H2 production by agar-immobilized cyanobacterium Aphanothece halophytica
(2019-10-01)
Pansook, Sunisa
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Incharoensakdi, Aran
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Phunpruch, Saranya
Cell immobilization is one of the techniques used to improve H<inf>2</inf> productivity in cyanobacteria. In this study, H<inf>2</inf> production by immobilized cells of unicellular halotolerant cyanobacterium Aphanothece halophytica was investigated and optimized. The results showed that immobilized cells of A. halophytica had higher H<inf>2</inf> production than free cells under nitrogen-deprived condition. Among various support material types used, agar-immobilized cells showed the highest H<inf>2</inf> production rate. Under nitrogen deprivation, the optimal conditions of cell immobilization for H<inf>2</inf> production were 3% (w/v) agar concentration, 0.2 mg dry cell weight per mL of gel solution, and 0.125 cm3 of agar cube. The optimum pH of medium and incubation temperature for H<inf>2</inf> production by agar-immobilized cells were pH 7.4 and 40 °C, respectively. Using a large glass vial and headspace volume resulted in enhancement of H<inf>2</inf> production by agar-immobilized cells. Finally, H<inf>2</inf> production by agar-immobilized cells was analyzed for three consecutive cycles. H<inf>2</inf> production could be maintained at the highest level after two cycles when half of immobilized cells were replaced with fresh immobilized cells. These findings indicate that the enhanced H<inf>2</inf> production of the unicellular halotolerant cyanobacterium A. halophytica can be achieved by immobilization method, thus providing the possibility to improve H<inf>2</inf> production by cyanobacteria in the future.
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Identification of bidirectional hydrogenase genes and their co-transcription in unicellular halotolerant cyanobacterium Aphanothece halophytica
(2016-04-01)
Phunpruch, Saranya
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Taikhao, Samart
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Incharoensakdi, Aran
The halotolerant cyanobacterium Aphanothece halophytica has been shown to produce H<inf>2</inf> via dark fermentation of accumulated glycogen under anoxic condition. One set of hox genes encoding a bidirectional hydrogenase is present in A. halophytica. In this study, the nucleotide sequence and the transcriptional analysis of hox genes in A. halophytica were investigated. The results revealed that A. halophytica contained five structural genes, hoxE, hoxF, hoxU, hoxY, and hoxH, without an insertion of other open reading frames (ORFs). The conserved cysteine motifs of iron-sulfur clusters involved in an electron transfer were found in all Hox subunits. The nucleotide and deduced amino acid sequences of hox genes in A. halophytica showed the highest identity and similarity to those of Halothece sp. PCC 7418. By reverse transcription polymerase chain reaction (RT-PCR) analysis, hox genes in A. halophytica were co-transcribed as a single operon. Under nitrogen-deprived condition, the transcripts of hoxH, glgB, coxA, ndhB, and psaA were upregulated whereas those of glgP and narB were downregulated which resulted in an increase of H<inf>2</inf> production, H<inf>2</inf>ase activity, glycogen content, and dark respiration rate.
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Factors affecting biohydrogen production by unicellular halotolerant cyanobacterium Aphanothece halophytica
(2013-04-01)
Taikhao, Samart
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Junyapoon, Suwannee
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Incharoensakdi, Aran
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Phunpruch, Saranya
The effects of several physiological parameters on H<inf>2</inf> production rate in the unicellular halotolerant cyanobacterium Aphanothece halophytica were investigated. Under nitrogen deprivation, the growth of cells was inhibited, but H<inf>2</inf> production rate was enhanced approximately fourfold. Interestingly, cells grown under sulfur deprivation exhibited a decrease in cell growth, H<inf>2</inf> production rate, and bidirectional hydrogenase activity. Glucose was the preferred sugar source for H<inf>2</inf> production by A. halophytica, but H<inf>2</inf> production decreased at high glucose concentrations. H<inf>2</inf> production rate was optimum when cells were grown in the presence of 0. 75 M NaCl, or 0. 4 μM Fe3+, or 1 μM Ni2+. The optimum light intensity and temperature for H<inf>2</inf> production were 30 μmol photons m-2 s-1 and 35 °C, respectively. A two-stage culture of A. halophytica was performed in order to overcome the reduction of cell growth in N-free medium. In the first stage, cells were grown in normal medium to accumulate biomass, and in the second stage, H<inf>2</inf> production by the obtained biomass was induced by growing cells in N-free medium supplemented with various chemicals for 24 h. A. halophytica grown in N-free medium containing various MgSO<inf>4</inf> concentrations had a high H<inf>2</inf> production rate between 11. 432 and 12. 767 μmol H<inf>2</inf> mg chlorophyll a (chl a)-1 h-1, a 30-fold increase compared to cells grown in normal medium. The highest rate of 13. 804 μmol H<inf>2</inf> mg chl a-1 h-1 was obtained when the N-free growth medium contained 0. 4 μM Fe3+. These results suggested the possibility of using A. halophytica and some other halotolerant cyanobacteria thriving under extreme environmental conditions in the sea as potential sources for H<inf>2</inf> production in the future. © 2012 Springer Science+Business Media B.V.

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