Energetic assessment of fixation of CO2 and subsequent biofuel production using B. cereus SM1 isolated from sewage treatment plant

Sustainable synergistic approach to chemolithotrophs-supported bioremediation of wastewater and flue gas

Flue gas emissions are the waste gases produced during the combustion of fuel in industrial processes, which are released into the atmosphere. These identical processes also produce a significant amount of wastewater that is released into the environment. The current investigation aims to assess the viability of simultaneously mitigating flue gas emissions and remediating wastewater in a bubble column bioreactor utilizing bacterial consortia. A comparative study was done on different growth media prepared using wastewater. The highest biomass yield of 3.66 g L-1 was achieved with the highest removal efficiencies of 89.80, 77.30, and 80.77% for CO2, SO2, and NO, respectively. The study investigated pH, salinity, dissolved oxygen, and biochemical and chemical oxygen demand to assess their influence on the process. The nutrient balance validated the ability of bacteria to utilize compounds in flue gas and wastewater for biomass production. The Fourier Transform-Infrared Spectrometry (FT-IR) and Gas Chromatography-Mass Spectrometry (GC-MS) analyses detected commercial-use long-chain hydrocarbons, fatty alcohols, carboxylic acids, and esters in the biomass samples. The nuclear magnetic resonance (NMR) metabolomics detected the potential mechanism pathways followed by the bacteria for mitigation. The techno-economic assessment determined a feasible total capital investment of 245.74$ to operate the reactor for 288 h. The bioreactor's practicability was determined by mass transfer and thermodynamics assessment. Therefore, this study introduces a novel approach that utilizes bacteria and a bioreactor to mitigate flue gas and remediate wastewater.

A comprehensive review of flue gas bio-mitigation: chemolithotrophic interactions with flue gas in bio-reactors as a sustainable possibility for technological advancements

Flue gas mitigation technologies aim to reduce the environmental impact of flue gas emissions, particularly from industrial processes and power plants. One approach to mitigate flue gas emissions involves bio-mitigation, which utilizes microorganisms to convert harmful gases into less harmful or inert substances. The review thus explores the bio-mitigation efficiency of chemolithotrophic interactions with flue gas and their potential application in bio-reactors. Chemolithotrophs are microorganisms that can derive energy from inorganic compounds, such as carbon dioxide (CO2), nitrogen oxides (NOx), and sulfur dioxide (SO2), present in the flue gas. These microorganisms utilize specialized enzymatic pathways to oxidize these compounds and produce energy. By harnessing the metabolic capabilities of chemolithotrophs, flue gas emissions can be transformed into value-added products. Bio-reactors provide controlled environments for the growth and activity of chemolithotrophic microorganisms. Depending on the specific application, these can be designed as suspended or immobilized reactor systems. The choice of bio-reactor configuration depends on process efficiency, scalability, and ease of operation. Factors influencing the bio-mitigation efficiency of chemolithotrophic interactions include the concentration and composition of the flue gas, operating conditions (such as temperature, pH, and nutrient availability), and reactor design. Chemolithotrophic interactions with flue gas in bio-reactors offer a potentially efficient approach to mitigating flue gas emissions. Continued research and development in this field are necessary to optimize reactor design, microbial consortia, and operating conditions. Advances in understanding the metabolism and physiology of chemolithotrophic microorganisms will contribute to developing robust and scalable bio-mitigation technologies for flue gas emissions.

Reforming CO2 bio-mitigation utilizing Bacillus cereus from hypersaline realms in pilot-scale bubble column bioreactor

The bubble column reactor of 10 and 20 L capacity was designed to bio-mitigate 10% CO2 (g) with 90% air utilizing thermophilic bacteria (Bacillus cereus SSLMC2). The maximum biomass yield during the growth phase was obtained as 9.14 and 10.78 g L-1 for 10 and 20 L capacity, respectively. The maximum removal efficiency for CO2 (g) was obtained as 56% and 85% for the 10 and 20 L reactors, respectively. The FT-IR and GC-MS examination of the extracellular and intracellular samples identified value-added products such as carboxylic acid, fatty alcohols, and hydrocarbons produced during the process. The total carbon balance for CO2 utilization in different forms confirmed that B. cereus SSLMC2 utilized 1646.54 g C in 10 L and 1587 g of C in 20 L reactor out of 1696.13 g of total carbon feed. The techno-economic assessment established that the capital investment required was $286.21 and $289.08 per reactor run of 11 days and $0.167 and $0.187 per gram of carbon treated for 10 and 20 L reactors, respectively. The possible mechanism pathways for bio-mitigating CO2 (g) by B. cereus SSLMC2 were also presented utilizing the energy reactions. Hence, the work presents the novelty of utilizing thermophilic bacteria and a bubble column bioreactor for CO2 (g) bio-mitigation.

In situ solvent recovery by using hydrophobic/oleophilic filter during wet lipid extraction from microalgae

While lipid extraction from wet microalgae has attracted attention as an economical method for microalgal biofuel production, few studies have focused the actual separation of extract phase from the emulsified extraction mixture. Here, a novel approach which utilizes hydrophobic/oleophilic filter was developed for the efficient solvent recovery. The filter was surface-modified by coating a functional polymer via initiated vapor deposition for the selective solvent permeability. While acid-treated Chlorella sorokiniana HS1 and n-hexane was stirred for lipid extraction, tubular filter module was immersed into the mixture for separation. The mixture was kept stirred during the separation to inhibit the buildup of cell debris on the filter by inducing crossflow on the filter. Extract phase was separated directly from the raffinate phase with high separation efficiency (> 98.3%) while maintaining permeation flux. The place-, space- and energy-efficient strategy reported here could be a useful tool for the solvent extraction process.