Isolating Fistulifera pelliculosa from the northern Bohai Sea and analyzing biochemical composition, antibacterial and nutrient removal potential

The microalgae located near the estuary of the Liaohe River along the coast of Panjin have long been in an area with large fluctuations in salinity, temperature, and nutrients, and have high-quality alternatives for high-value metabolites. Three strains of microalgae were screened and the biomass of microalgae could be optimized 0.313-0.790 g L^-1 in 10 L bioreactor. The determination results of bioactive substances in these three microalgae showed that, the amount of fucoxanthin in the growth phase II (14 days) was maximum, at 5.354, 6.284 and 14.837 mg g^-1 respectively. The diatoxanthin of Dut-wj-J1 in growth phase III (21 days) could reach 5.158 mg g^-1. Dut-wj-J4 had the highest lipid production efficiency (9.45 mg L^-1 d^-1) followed by Dut-wj-J2 (8.49 mg L^-1 d^-1) and Dut-wj-J1 (8.18 mg L^-1 d^-1) respectively. These bioactive substances have inhibition zones of 7-13 mm against all four strains of bacteria ie., Acetobacter, Rhodococcus erythropolis, Escherichia coli and Bacillus subtilis Cohn respectively. In addition, these microalgae can play a potential role in nutrient enrichment in eutrophic seawater. The NO₃^- degradation rates of these three algae in the first 14 days were 75.0 %, 45.8 % and 100 % respectively, as well as the PO₄^- degradation rates in the first 7 days were 94.8 %, 100 % and 80.9 % respectively. This work manifests the plasticity of algae isolated from the Bohai Sea and provides useful insights for further joint production of bioactive substances.

Measuring the effects of diethyl phthalate microplastics on marine algae growth using dielectric spectroscopy

This paper presents the development of a dielectric spectroscopy-based method using a customized, transmission line probe, fabricated on a printed circuit board (PCB), for monitoring the effect of diethyl phthalate (DEP) microplastics on marine algae growth. Experiments were performed by exposing marine algae (Chlorella pyrenoidosa) to DEP (0-50 mg) for up to 6 days. In order to amplify the electrophysiological effects and improve the sensing, a glutaraldehyde crosslinking agent was used and encapsulated on the surface of the probe. The reflection coefficient (S₁₁) and the complex permittivity (ɛ' & ɛ″) of the Medium Under Test (MUT) were investigated in the frequency range of 30 kHz-800 MHz. Without the presence of DEP, the number of algae (10⁴ cells/mL) and chlorophyll content (mg/L) increased at the rates of 207.73 × 10⁴ cells/mL and 148.1 mg/L per day, respectively. After 6 days of exposing Chlorella pyrenoidosa (C. pyrenoidosa) algae to different DEP concentrations, the growth rate decreased down to -11.92 × 10⁴ cells/mL and -19.19 mg/L (50 mg DEP), respectively. Additionally, the linearity of the relationship kept decreasing as the DEP content increased from R² = 0.9716 to R² = 0.1050 and from R² = 0.9293 to R² = 0.4961, respectively. Dielectric spectroscopy using the custom, transmission line probe, at 740 MHz, showed linear relationship (-1.22 dB/day) between the reflection coefficient (S₁₁) and hence complex permittivity (ɛ' & ɛ″) without the presence of DEP. However, as the DEP content increased, algae growth was prohibited more intensely, shown both from the number of algae and the chlorophyll content. This trend was reflected on S₁₁ and subsequently on the complex permittivity. This relationship confirms the capability of this method to monitor the growth of marine algae in almost real-time. This dielectric spectroscopy method could be a potential, low-cost tool to examine the impact of microplastic pollutants on marine microorganisms.

Enhanced removal of tetracycline from synthetic wastewater using an optimal ratio of co-culture of Desmodesmus sp. and Klebsiella pneumoniae

A sustainable approach of Desmodesmus sp. GIEC-179: Klebsiella pneumoniae (DUT-XJR-t-1.2) co-culture ratios were optimized to remove tetracycline (TET) from synthetic wastewater. To enhance the tetracycline removal performance, the effect of microalgae-bacterial co-culture ratio, maximum TET concentration, effective inoculum amount, growth temperature and pH were studied. The optimized ratio 1:2 of Desmodesmus sp.: K. pneumoniae showed the optimal removal percentage at the temperature of 25 °C, pH 7 and 10% inoculum amount; and the removal of TET was recorded as 95%. Moreover, this study explored the Desmodesmus sp.: K. pneumoniae (1:2) nutrient (COD, NH₄⁺ and PO₄^3-) exchange relationship and their interaction of TET removal to better understand their fundamental mechanism. According to the results of this study, Desmodesmus sp.: K. pneumoniae co-culture could be a green option for bio-removal of tetracycline from wastewater.