Enrichment, characterization, and sand consolidation application of urease active calcite-producing bacteria.

Minerals such as calcium carbonate, which is prevalent in marble and limestone, are present naturally in rocks. Both physicochemical processes and microbial processes can result in the creation of calcium carbonate in nature, as is well documented. In this study, microbiologically induced calcite precipitation potential of three different Travertine-type water sources (Pamukkale Travertine Spring (PTS), Pamukkale Travertine Terraces (PTT), and Red Travertine of Karahayit (RTK)) using three different incubation media (NB, NB3, and ATCC1832) were investigated. After enrichment with ATCC1832 media, urease assays were positive for all of the microbial sources. The PTS and PTT were cultured with ATCC1832 medium for 48 h, which showed the best results for urease activity and microbial growth among other samples. Metagenome analyses indicated that PTT enriched with ATCC1832 media contains > 99% Firmicutes, while PTS enriched with ATCC1832 contains > 99% Proteobacteria at the Phylum level. Results from SEM-EDX and XRD analysis revealed that calcite and/or vaterite were the minerals that emerged from the mineralization of the PTS and PTT during incubation. The type of calcium carbonate crystals tended to change from one form to another when the incubation period extends from 72 to 120 h. Both the PTS and the PTT were able to precipitate calcite within the sand column. However, the bacteria from the PTT (26% CaCO3) outperformed those from the PTS (18% CaCO3) in terms of calcium carbonate deposition on the 21st day of incubation.

Prediction of biogas production of industrial scale anaerobic digestion plant by machine learning algorithms.

In the anaerobic digestion (AD) process there are some difficulties in maintaining process stability due to the complexity of the system. The variability of the raw material coming to the facility, temperature fluctuations and pH changes as a result of microbial processes cause process instability and require continuous monitoring and control. Increasing continuous monitoring, and internet of things applications within the scope of Industry 4.0 in AD facilities can provide process stability control and early intervention. In this study, five different machine learning (ML) algorithms (RF, ANN, KNN, SVR, and XGBoost) were used to describe and predict the correlation between operational parameters and biogas production quantities collected from a real-scale anaerobic digestion plant. The KNN algorithm had the lowest accuracy in predicting total biogas production over time, while the RF model had the highest prediction accuracy of all prediction models. The RF method produced the best prediction, with an R2 of 0.9242, and it was followed by XGBoost, ANN, SVR, and KNN (with R2 values of 0.8960, 0.8703, 0.8655, 0.8326, respectively). Real-time process control will be provided and process stability will be maintained by preventing low-efficiency biogas production with the integration of ML applications into AD facilities.

Reuse of sea water reverse osmosis brine to produce Dunaliella salina based ß-carotene as a valuable bioproduct: A circular bioeconomy perspective.

Due to population growth and global warming, the use of the sea water reverse osmosis process to obtain freshwater is increasing rapidly. A sustainable method with low environmental impact is limited for the management of brine with a high salt content, which is released as a result of the process. Some microalgae species can grow in salty environments and produce ß-carotene. This study aims to evaluate the commercial potential of ß-carotene production from microalgae grown in sea water reverse osmosis brine from a bioeconomy perspective. Synthetic media are often used for the production of ß-carotene from algae, the use of sea water reverse osmosis brine is not common and the commercial potential of this application has not been evaluated before. In terms of the development of the ß-carotene market, the strengths and weaknesses of the process, opportunities, and threats are thoroughly examined in this report. Also, with the use of sea water reverse osmosis, a daily 750 tons of algal ß-carotene can be produced. The biotechnological production of microalgal ß-carotene and the reuse of salt water within the scope of circular bioeconomy are seen as a sustainable solution due to the fact that the strengths of the process are dominant, and the market value of natural ß-carotene is increasing day by day.

Optimization of liquid fertilizer production from waste seaweed: A design of experiment based statistical approach.

In Istanbul, which is surrounded by the sea on 3 sides, thousands of tons of seaweed that have formed naturally every year are washed ashore. In this study, the usability of these seaweeds which are landfilling already in fertilizer production was discussed. Liquid fertilizer production was carried out using 3 different physical and 4 different biological methods, and the produced fertilizers were diluted in 5 different ratios (1%, 10%, 25%, 50%, and 100%) and applied to cress seed. The effect of each fertilizer and its concentration on seed germination, plant length, number of leaves, and soil moisture-holding capacity was studied. The data obtained were analyzed using Response Surface Methodology (RSM). The results showed that if seaweed was fermented with anaerobic seed sludge for 15 days and applied to the plant by diluting it to 15-25%, plant growth will be supported at an optimum level. It has also been shown that if the seaweed was fermented with yeast culture for 18 days and fed with a concentration of >90%, the moisture-holding capacity of the soil could be increased by up to 27%.

Determination of photoautotrophic growth and inhibition kinetics by the Monod and the Aiba models and bioenergetics of local microalgae strain.

The usage of fossil fuels results in a high amount of greenhouse gas (GHG) emissions and renewable green energy requirements entail saving ecological balance. Therefore, microalgae cultivation is widespread as a suitable raw material to produce renewable and sustainable fuel. Mathematical models are useful tools for the estimation of different conditions of a system. In this study, mathematical models were developed for monitoring the cultivation of local species of microalgae based on the chlorophyll-a and biomass concentration. Coefficients that were calculated from the Monod kinetic model were µmax; 0.03 day-1, KS, Ci; 0.53 mM with an R2 value of 0.93 and from the Aiba inhibition kinetic model was µmax and KS, Ci 1.48 day-1 and 0.08 mM with an R2 value of 0,73. According to the literature, there was no model was developed for the determination of kinetic coefficients based on chlorophyll-a production due to the inorganic carbon consumption. While both growth and inhibition models were developed for the inorganic carbon consumption, chlorophyll-a concentration was used for the growth model and biomass concentration was used for the inhibition model which caused and directly affected by the decrease of light penetration. The maximum biomass and chlorophyll-a concentrations were found as 1.2 g/L and 27.8 mg/L respectively with 10.24 mg/L. day-1 nitrogen and 1.19 mg/L.day-1 phosphorus uptake rate.

A multicriteria decision analysis for the evaluation of microalgal growth and harvesting.

Biomass obtained from microalgae research studies gained momentum in recent years because of their extensive application potential in multiple industries such as high-value nutraceuticals, bioproducts, cosmetics, animal feed industries, and biofuels while being a sustainable and environmentally friendly option. Although they have high biomass yields and rapid growth rates there are some limitations and challenges that remain for large-scale commercialized cultivation and harvesting methods of microalgae. Since there are multiple pathways related to efficient cultivation and harvesting methods to be viable, this study adopted, TOPSIS (Technique for Order Preference by Similarity to Ideal Solution), a multicriteria decision-making tool, to find the most acceptable alternative by using excel spreadsheets to evaluate the information that is derived from literature and pilot-scale studies. As a result, tubular (helical) and plate (flat panel) photobioreactors (PBRs) for cultivation and chemical harvesting (with chitosan) and bio-flocculation for harvesting were deemed suitable, while plastic bag PBR and suspended air flotation were deemed unsuitable.

Fluidized bed bioreactor for multiple environmental engineering solutions.

Fluidized bed bioreactors (FBR) are characterized by two-phase mixture of fluid and solid, in which the bed of solid particles is fluidized by means of downward or upward recirculation stream. FBRs are widely used for multiple environmental engineering solutions, such as wastewater treatment, as well as some industrial applications. FBR offers many benefits such as compact bioreactor size due to short hydraulic retention time, long biomass retention on the carrier, high conversion rates due to fully mixed conditions and consequently high mass transfer rates, no channelling of flow, dilution of influent concentrations due to recycle flow, suitability for enrichment of microbes with low Km values. The disadvantages of FBRs include bioreactor size limitations due to the height-to-diameter ratio, high-energy requirements due to high recycle ratios, and long start-up period for biofilm formation. This paper critically reviews some of the key studies on biomass enrichment via immobilisation of low growth yield microorganisms, high-rates via fully mixed conditions, technical developments in FBRs and ways of overcoming toxic effects via solution recycling. This technology has many potential new uses as well as hydrodynamic characteristics, which enable high-rate environmental engineering and industrial applications.

Electricity Production and Characterization of High-Strength Industrial Wastewaters in Microbial Fuel Cell.

Microbial fuel cells (MFCs) convert electrochemical energy into electrical energy immediately and have a big potential usage for the same time wastewater treatment and energy recovery via electro-active microorganisms. However, MFCs must be efficiently optimized due to its limitations such as high cost and low power production. Finding new materials to increase the cell performance and reduce cost for MFC anodes is mandatory. In the first step of this study, different inoculation sludges such as anaerobic gum industry wastewater, anaerobic brewery wastewater and anaerobic phosphate were tested, and MFC that was set up with anaerobic gum industry wastewater inoculation sludge exhibited the highest performance. In the second step of this study, various wastewaters such as chocolate industry, gum industry and slaughterhouse industry were investigated for anode bacteria sources. Several electrochemical techniques have been employed to elucidate how wastewaters affect the MFCs' performance. Among all the mentioned wastewaters, the best performance was achieved by the MFCs fed with slaughterhouse wastewater; this device produced a maximum power density of 267 mW·m-2.

Simultaneous production of bioelectricity and treatment of membrane concentrate in multitube microbial fuel cell.

The performance of upflow multitube microbial fuel cell (UM2FC) from membrane concentrate of domestic wastewater (50% concentrate or a volume to concentration ratio of 2) has been investigated in a laboratory test. The test found that the UM2FC with the tin-coated copper mesh and coil spring under different hydraulic retention times (HRTs) produced maximum electricity of 916 ± 200 mW/m3 (61 mW/m2) at an HRT of 0.75 day with a 78% soluble chemical oxygen demand (sCOD) removal efficiency and 3% and 20% Coulombic efficiencies (CEs). The whole-cell resistance as calculated from the Nyquist plot and equivalent circuit were approximately 134 and 255 Ω for HRTs of 0.5 and 0.75 days, respectively. Considering HRT, the current increase with longer HRT could be due to longer contact time between organic material and biofilm, which results in a higher electrical efficiency. The results showed that UM2FC could represent an effective system for simultaneous membrane concentrate treatment and electricity production after further improvements on MFC and operating conditions.

The development of catalytic performance by coating Pt-Ni on CMI7000 membrane as a cathode of a microbial fuel cell.

Performance of cathode materials in microbial fuel cell (MFC) from dairy wastewater has been investigated in laboratory tests. Both cyclic voltammogram experiments and MFC tests showed that Pt-Ni cathode much better than pure Pt cathode. MFC with platinum cathode had the maximum power density of 0.180 W m(-2) while MFC with Pt:Ni (1:1) cathode produced the maximum power density of 0.637 W m(-2), even if the mass mixing ratio of Pt is lower in the alloy were used. The highest chemical oxygen demand (COD) removal efficiency was around 82-86% in both systems. The cyclic voltammogram (CV) analyses show that Pt:Ni (1:1) offers higher specific surface area than Pt alone does. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) results showed that entire Pt:Ni (1:1) alloys can reduce the oxygen easily than pure platinum, even though less precious metal amount. The main outcome of this study is that Pt-Ni, may serve as a alternative catalyst in MFC applications.