Dark fermentative hydrogen production and transcriptional analysis of genes involved in the unicellular halotolerant cyanobacterium Aphanothece halophytica under nitrogen and potassium deprivation

The unicellular halotolerant cyanobacterium Aphanothece halophytica is known as a potential hydrogen (H2) producer. This study aimed to investigate the enhancement of H2 production under nutrient deprivation. The results showed that nitrogen and potassium deprivation induced dark fermentative H2 production by A. halophytica, while no differences in H2 production were found under sulfur and phosphorus deprivation. In addition, deprivation of nitrogen and potassium resulted in the highest H2 production in A. halophytica due to the stimulation of hydrogenase activity. The effect of adaptation time under nitrogen and potassium deprivation on H2 production was investigated. The results showed that the highest H2 accumulation of 1,261.96 ± 96.99 µmol H2 g dry wt−1 and maximum hydrogenase activity of 179.39 ± 8.18 µmol H2 g dry wt−1 min−1 were obtained from A. halophytica cells adapted in the nitrogen- and potassium-deprived BG11 medium supplemented with Turk Island salt solution (BG110-K) for 48 h. An increase in hydrogenase activity was attributed to the decreased O2 concentration in the system, due to a reduction of photosynthetic O2 evolution rate and a promotion of dark respiration rate. Moreover, nitrogen and potassium deprivation stimulated glycogen accumulation and decreased specific activity of pyruvate kinase. Transcriptional analysis of genes involved in H2 metabolism using RNA-seq confirmed the above results. Several genes involved in glycogen biosynthesis (glgA, glgB, and glgP) were upregulated under both nitrogen and potassium deprivation, but genes regulating enzymes in the glycolytic pathway were downregulated, especially pyk encoding pyruvate kinase. Interestingly, genes involved in the oxidative pentose phosphate pathway (OPP) were upregulated. Thus, OPP became the favored pathway for glycogen catabolism and the generation of reduced nicotinamide adenine dinucleotide phosphate (NADPH), which resulted in an increase in H2 production under dark anaerobic condition in both nitrogen- and potassium-deprived cells

Free Radical Scavenging Properties and Induction of Apoptotic Effects of Fa Fraction Obtained after Proteolysis of Bioactive Peptides from Microalgae Synechococcus sp. VDW

Svrha ovog istraživanja bila je odrediti antioksidacijsku aktivnost bioaktivnih peptida izoliranih iz stanica mikroalge Synechococcus sp. VDW nakon 21 dana uzgoja. Hidrolizati proteina iz mikroalge Synechococcus sp. VDW dobiveni su pomoću tripsina, te su zatim pročišćeni ultrafiltracijom pomoću membrana veličine od 10, 5 i 3 kDa. Frakcija proteina FA molekularne mase od 3 kDa imala je najveću sposobnost uklanjanja slobodnih radikala 2,2\u27-azino-bis(3-etilbenzotiazolin-6-sulfonske kiseline) (ABTS), IC50 vrijednosti od (11,5±0,3) μg/mL, i 2,2\u27-difenil-1-pikrilhidrazila (DPPH), IC50 vrijednosti od (13,6±0,2) μg/mL. Frakcija proteina FA razdvojena je pomoću HPLC kromatografije obrnutih (reverznih) faza u četiri podfrakcije (F1–4). Subfrakcija F4 imala je maksimalni učinak uklanjanja ABTS radikala od (3,55±0,61) %, pa je odabrana za daljnju analizu pomoću metode ESI-Q-TOF-MS/MS, temeljene na sekvenciranju peptida de novo. Identificirano je pet peptida s antioksidacijskim učinkom, od kojih je najveću sposobnost uklanjanja ABTS radikala imao peptid AILESYSAGKTK. Nadalje, frakcija FA imala je snažan citotoksični učinak na stanične linije humanih karcinoma, pogotovo staničnu liniju raka debelog crijeva (SW620), pri čemu je IC50 vrijednost bila (106,6±21,5) μg/mL, no nije imala citotoksični učinak na netransformiranu staničnu liniju Wi38. Uzrokovala je početak apoptoze u staničnoj liniji SW620 nakon 24, 48 i 72 sata, s najvećom aktivnosti kaspaza 3, 8 i 9 nakon 72 sata. Dobiveni rezultati pokazuju da se mikroalga Synechococcus sp. VDW može upotrijebiti za proizvodnju prirodnih antitumorskih lijekova.This study aims to determine the antioxidant activity of bioactive peptides derived from Synechococcus sp. VDW cells cultured for 21 days. Synechococcus sp. VDW protein hydrolysates were prepared with trypsin and purified by ultrafiltration with molecular mass cut-off membranes of 10, 5 and 3 kDa. The M<3 kDa (FA) fraction had the highest 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities, with IC50 values of (11.5±0.3) and (13.6±0.2) µg/mL, respectively. The FA fraction was separated by reversed phase HPLC to yield four subfractions (F1–4). The F4 subfraction showed the highest maximum ABTS radical scavenging activity (3.55±0.61) % and it was selected for further analysis by electrospray ionisation quadrupole time-of-flight mass spectrometry (ESI-Q-TOF-MS/MS) based on de novo peptide sequencing. Five antioxidant peptides were identified, of which AILESYSAGKTK had the highest ABTS radical scavenging activity. Furthermore, the FA fraction showed high cytotoxic activities against human cancer-derived cell lines, especially the colon cancer cell line (SW620) with an IC50 value of (106.6±21.5) µg/mL, but not the untransformed Wi38 cell line. The FA fraction activated the apoptotic pathway in SW620 cells after treatment for 24, 48 and 72 h, with the highest activities of caspases-3, -8 and -9 being observed after treatment for 72 h. These findings suggested that microalgae Synechococcus sp. VDW may be used to develop natural anticancer drugs

Cellular lipid production of a heterotrophic bacterium isolated from poultry processing wastewater

Cell growth and lipid production of a heterotrophic bacterium, R4.4 which accumulated the highest lipid content among 12 bacterial colonies being isolated from wastewater of a poultry processing plant in Thailand, were evaluated in this study. The culture was identified as Aeromonas sp. by 16S ribosomal DNA sequencing analysis.The highest lipid content was obtained when the cells were in the early stationary growth phase compared to the cells in the exponential and the late stationary phase. Over 50% of the fatty acid production by Aeromonas sp. KMITL-R4.4 were unsaturated fatty acids, including linoleic acid (C18:2, 43.2%), oleic acid (C18:1, 19.0%), and palmitoleic acid (C16:1, 8.2%). The culture had a preference for glucose and fructose as seen from the maximum biomass and lipid contents that were obtained. Among volatile fatty acid (VFA) species tested, acetic acid was the preferred substrate for lipid production but not favorable for cell growth. In addition, ammonium sulfate was found to be the best among nitrogen sources tested. The C/N ratio exerts significant impact on lipid production as seen from an increase of the lipid content from 10.8% to 18.2% by exposing the bacterial cells to a medium with lower nitrogen concentration (0.1g/l) and higher level of glucose (28 g/l)

Distribution of hsp65 PCR-Restriction Enzyme Analysis Patterns among Mycobacterium avium Complex Isolates in Thailand

A total of 227 clinical Mycobacterium avium complex isolates from Thailand were differentiated into species and types by using PCR-restriction enzyme analysis of hsp65. The distribution of types showed the predominance of M. avium I (77%) in blood specimens, whereas M. intracellulare I was more commonly found in pulmonary specimens (44.2%). In addition, infections with M. avium were more likely to be found in younger adults (20 to 39 years old), while infections with M. intracellulare were more likely to be found in older adults (≥60 years old). Our results provide the useful epidemiological information that some particular types have more invasive and virulent characters than others