Microalgal-Bacterial Consortia as Future Prospect in Wastewater Bioremediation, Environmental Management and Bioenergy Production

Development of autotrophic and heterotrophic consortia via immobilized microbial beads for chemical wastewater treatment, using PTA wastewater as an approach

Studies on the symbiosis of microalgae-bacteria have been accelerating as a mean for wastewater remediation. However, there were few reports about the microalgae-bacteria consortia for chemical wastewater treatment. The aim of the present study is to develop an autotrophic and heterotrophic consortium for chemical wastewater treatment and probe whether and how bacteria could benefit from the microalgae during the treatment process, using PTA wastewater as an approach. A process-dependent strategy was applied. First of all, the results showed that the sludge beads with the sludge concentration of 30 g/L were the optimal one with the COD removal rate at 84.8% but the ceiling effect occurred (COD removal rate < 90%) even several common reinforcement methods were applied. Additionally, by adding the microalgae Chlorella vulgaris, a microalgae-activated sludge consortium was formed inside the immobilized beads, which provided better performance to shatter the ceiling effect. The COD remove rate was higher than 90%, regardless of the activated sludge was pre-culture or not. COD removal capacity could also be improved (COD removal rate > 92%) when LEDs light belt was offered as an advanced light condition. Biochemical assay and DNA analysis indicated that the microalgae could form an internal circulation of substances within the activated sludge and drove the microbial community to success and the corresponding gene functions, like metabolism and.

Ethanol Production from Colpomenia sinuosa by an Alginate Fermentation Strain Meyerozyma guilliermondii

With the consumption of energy and the spread of COVID-19, the demand for ethanol production is increasing in the world. The industrial ethanol fermentation microbes cannot metabolize the alginate component of macro algae, which affects the ethanol yield. In this research, the ethanol production process from macro algae by an alginate fermentation yeast Meyerozyma guilliermondii, especially the pretreatment process of Colpomenia sinuosa, was studied. At the same time, the experimental design of Box-Behnken was carried out to achieve the optimum fermentation performance. The concentration of KH₂PO₄ (A: 2-6 g.L^-1), pH (B: 4-7), reaction time (C: 60-120 h) and temperature (D: 24-34 °C) were variable input parameters. During the ethanol production process, the algae powder was firstly mixed with water at 90 °C for 0.5 h. Later the fermentation culture medium was prepared and then it was fermented by the yeast Meyerozyma guilliermondii to produce ethanol. And the optimal fermentation parameters were as follows: fermentation temperature of 28 °C, KH₂PO₄ dosage of 4.7 g.L^-1, initial pH of 6, and fermentation time of 99 h. The ethanol yield reached 0.268 g.g^-1 (ethanol to algae), close to the predicted value of model. The generation of alginate lyase during the fermentation of algae was also examined. The highest alginate lyase activity reached 46.42 U.mL^-1.

Immobilized Microalgae-Based Photobioreactor for CO2 Capture (IMC-CO2PBR): Efficiency Estimation, Technological Parameters, and Prototype Concept

Microalgae-mediated CO2 sequestration has been a subject of numerous research works and has become one of the most promising strategies to mitigate carbon dioxide emissions. However, feeding flue and exhaust gas into algae-based systems has been shown to destroy chloroplasts, as well as disrupt photosynthesis and other metabolic processes in microalgae, which directly limits CO2 uptake. CO2 biosequestration in existing photobioreactors (PBRs) is also limited by the low biomass concentration in the growth medium. Therefore, there is a real need to seek alternative solutions that would be competitive in terms of performance and cost-effectiveness. The present paper reports the results of experiments aimed to develop an innovative trickle bed reactor that uses immobilized algae to capture CO2 from flue and exhaust gas (IMC-CO2PBR). In the experiment, ambient air enriched with technical-grade CO2 to a CO2 concentration of 25% v/v was used. The microalgae immobilization technology employed in the experiment produced biomass yields approximating 100 g DM/dm3. A relationship was found between CO2 removal rates and gas volume flux: almost 40% of CO2 was removed at a feed of 25 dm3 of gas per hour, whereas in the 200 dm3/h group, the removal efficiency amounted to 5.9%. The work includes a determination of basic process parameters, presentation of a developed functional model and optimized lighting system, proposals for components to be used in the system, and recommendations for an automation and control system for a full-scale implementation.