Bioprocess and Biosystems Engineering最新文献

This study aimed to evaluate different methods of recovery of carotenoid-rich microbial oil (CRMO) produced by Rhodotorula mucilaginosa in renewable agro-industrial by-products to achieve oleogels based on CRMO and carnauba wax (CW). Among the oil extraction methods, Bligh and Dyer was selected since this system kept color stability. Extracted CRMO showed 41.1 µg g^-1 of total carotenoid and lipid content of 23.8%. Oleogels based on CRMO or olive oil (control system) and CW at concentrations of 2.5, 5, 7.5, and 10% were characterized and their potential application to food systems was highlighted. This study is one of the first to describe production of oleogel based on CRMO. Its results contribute to its potential as a fat replacer. This novel oleogel may meet worldwide demands to reduce trans fatty acids in foods and act as a protective system of bioactive biocompounds.

Electric stimulation (ES) is a versatile technique that uses an electric field to manipulate microorganisms individually. Over the past several decades, the capabilities of ES have expanded from bioremediation to the precise motion control of cells and microorganisms. However, there is limited information on the underlying mechanisms, latest advancement and broader microbial applications of ES in various fields, such as the production of extracellular polymers with upgraded properties. This review article summarizes recent advancements in ES and discusses it as a unique external manipulation technique for microorganisms with wide applications in bioremediation, industry, biofilm deactivation, disinfection, and controlled biosynthesis. One specific application of ES discussed in this review is the extracellular biosynthesis, regulation, and organization of extracellular polymers, such as bacterial cellulose nanofibrils, curdlan, and microbial nanowires. Overall, this review aims to provide a platform for microbial biotechnologists and synthetic biologists to leverage the manipulation of microorganisms using ES for bio-based applications, including the production of extracellular polymers with enhanced properties. Researchers can engineer, manipulate, and control microorganisms for various applications by harnessing the potential of electric fields.

The present study investigated effects of coupling electrocoagulation (EC) process with an anaerobic digestion bioreactor, namely up-flow anaerobic sludge blanket (UASB), for the synthetic wastewater treatment. The EC-UASB mode of operation consisted of one anode and two cathodes subjected to an intermittent electrical current (10 min ON/30 min OFF) with current density of 1.5 mA/cm². In light of this integration, the concentration of mixed liquor suspended solids and mixed liquor volatile suspended solids within anaerobic granular sludge (AGS) increased by 20.0 ± 1.4% and 12.8 ± 0.8%, respectively. The results of sludge volume index, loosely and tightly bound extracellular polymeric substances and their constituents (protein and carbohydrate) revealed that through this integration the quality of AGS has been improved. Furthermore, results of scanning electron microscopy and Fourier-transform infrared spectroscopy showed alteration in the morphology and functional groups of AGS, respectively. Additionally, this combination has demonstrated promising results in terms of performance improvement by increasing the removal efficiency of total dissolved solids by 12.1 ± 0.3% and reducing the ionic pollution in treated wastewater. However, the integration of the EC system within the UASB resulted in energy consumption and operating cost of 1.33 kWh/m³ and 0.099 USD/m³, respectively.

Droplet-based bioprinting (DBB) allows for high precision, noncontact, and on-demand distribution of bioinks, hence it has been widely utilized in the preparation of bacteria-laden living materials (BLMs). Nonetheless, discontinuous ink deposition makes it challenging to fabricate large-sized intact living structures via this technique. Herein, we explore the way of using DBB to construct centimeter-scale BLMs with bespoke geometries, and further demonstrate its potential applicability in sensing-responsive device by integrating engineered bacteria. We first established a DBB method based on printing-path design, which does not require hardware modification. This strategy was able to produce customized 3D-hydrogel structures with high shape fidelity. Then, we confirmed the excellent biocompatibility of the above biofabrication approach. The Escherichia coli survived 93% ± 4.0% in printed BLMs, with uniform distribution throughout the structure. As a proof-of-concept, we finally manufactured a test strip-like heavy metal biosensor capable of plug-and-play detecting mercury (II) in water using the aforesaid approach. To our knowledge, this is the first study to employ 3D bioprinted BLMs for the detection of prevalent heavy metal pollutants. Our research shed light on the versatility of DBB in BLMs construction, which is not restricted to two-dimensional patterns. Moreover, our results are expected to innovate heavy metal biodetection and improve detection efficiency and sensitivity.

D-pantothenate, universally acknowledged as vitamin B5, has garnered considerable interest owing to its crucial functionality in the feed, pharmaceutical, and cosmeceutical sectors. Development of microbial strains for D-pantothenate hyperproducer has emerged as a prominent research direction in recent years. Herein, we converted an engineered Escherichia coli with low yield to a plasmid-free hyperproducer of D-pantothenate using multiplex combinatorial strategies. First, an initial strain was obtained through prolonging the cell lifespan. To promote the accumulation of D-pantothenic acid, the supply of cofactors was adaptively enhanced. Additionally, the heterologous gene panE from Pseudomonas aeruginosa, which encodes ketopantoate reductase (EC 1.1.1.169) catalyzing the synthesis of d-pantoate from α-ketopantoate, was screened and integrated into the chromosome. Subsequently, a strategy of acetate recycling and NOG pathway reconstruction were introduced and successfully to improve the D-pantothenate titer to 5.48 g/L. Additionally, we screened the regulatory factors and optimized its second codon to further increase the DPA yield of the engineered strains to 6.02 g/L in shake flask. The final engineered strain DS6 could efficiently produce 72.40 g/L D-pantothenate, which is 3.18-fold higher than the original strain. This study proposed a novel multiplex combination strategy for developing microbial cell factory of D-pantothenate, which was beneficial for the advancement of efficient D-pantothenate production.

The efficient and eco-friendly removal of lignin is a critical challenge for bioethanol production from lignocellulosic biomass. Herein, we report the integration of laccase with deep eutectic solvents (DESs) for the pretreatment of corn stover to enhance the production of reducing sugars. Three betaine-based DESs were prepared and tested for their effects on the activity and stability of a bacterial laccase from Bacillus amyloliquefaciens LC02. The aqueous solution of DESs showed no adverse influence on laccase activity, and the laccase thermostability was improved in the presence of DESs. More than 95% of the laccase activity was retained in the DESs solution during the first hour of incubation at 70 °C. A red shift in the fluorescence spectra was observed for the laccase in the presence of DESs, indicating conformational changes. The laccase was able to degrade a dimeric lignin model compound by cleaving its β-O-4 bond. The transformation products were identified using LC-MS. The maximal lignin removal from corn stover was achieved by pretreatment using laccase in combination with the betaine-glycerol DES, which also resulted in a yield of fermentable sugar that was 130% higher than the control. This combination strategy provides guidance on the application of laccase and DESs in the pretreatment of lignocellulosic biomass.

The study focused on rhamnolipid production by batch fermentation of Pseudomonas aeruginosa USM-AR2 in a 3-L stirred-tank reactor (STR) using palm sludge oil (PSO) as the sole carbon source. The impact of various agitation rates towards the dispersion of PSO in the medium was evaluated to improve biomass growth and rhamnolipid production. A mechanical foam collection and recycling system was designed and retrofitted to the STR to overcome severe foam formation during fermentation. The maximum biomass produced was 11.29 ± 0.20 g/L obtained at 400 rpm, while the maximum rhamnolipid production was 5.06 ± 1.17 g/L at 600 rpm, giving a rhamnolipid productivity of 0.023 g/L/h. High agitation enhances substrate availability by breaking the hydrophobic semi-solid PSO into smaller substrate particles, increasing surface contact area, thus facilitating the PSO utilisation by P. aeruginosa USM-AR2, thereby inducing rhamnolipid production. This study further demonstrates the ability of rhamnolipid to solubilize and disperse sludge oil, which typically remains a solid at room temperature, in the liquid medium. GCMS analysis showed that five fatty acids, namely palmitic acid, myristic acid, stearic acid, methyl ester and linoleic acid, have been utilised. The rhamnolipid showed an oil spreading test result of 160 mm of waste engine oil displacement compared to control using distilled water that remained non-displaced, and a critical micelle concentration (CMC) of 17 mg/L. In emulsification index (E₂₄) assay, the rhamnolipid was shown to emulsify toluene (66.7% ± 7.2), waste engine oil (58.3% ± 7.2), kerosene (41.8% ± 4.8) and n-hexane (33.1% ± 5.7). UPLC analysis on rhamnolipid revealed a congener mixture of rhamnolipid, namely di-rhamnolipid and mono-rhamnolipid mixture. This is the first report on the employment of an integrated foam control reactor system with PSO as the carbon source for rhamnolipid production by P. aeruginosa USM-AR2 culture.

The present study aims to analyze the interaction between Rhodotorula toruloides and magnetic nanoparticles and evaluate their effect on carotenoid production. The manganese ferrite nanoparticles were synthesized without chitosan (MnFe₂O₄) and chitosan coating (MnFe₂O₄-CS) by the co-precipitation method assisted by hydrothermal treatment. XRD (X-ray diffraction), Magnetometry, Dynamic Light Scattering (DLS) and FTIR (Fourier-Transform Infrared Spectroscopy), are used to characterize the magnetic nanoparticles. The crystallite size of MnFe₂O₄ was 16 nm for MnFe₂O₄ and 20 nm for MnFe₂O₄-CS. The magnetic saturation of MnFe₂O₄-CS was lower (39.6 ± 0.6 emu/g) than the same MnFe₂O₄ nanoparticles (42.7 ± 0.3 emu/g), which was attributed to the chitosan fraction presence. The MnFe₂O₄-CS FTIR spectra revealed the presence of the characteristic chitosan bands. DLS demonstrated that the average hydrodynamic diameters were 344 nm for MnFe₂O₄ and 167 nm for MnFe₂O₄-CS. A kinetic study of cell immobilization performed with their precipitation with a magnet demonstrated that interaction between magnetic nanoparticles and R. toruloides was characterized by an equilibrium time of 2 h. The adsorption isotherm models (Langmuir and Freundlich) were fitted to the experimental values. The trypan blue assay was used for cell viability assessment. The carotenoid production increased to 256.2 ± 6.1 µg/g dry mass at 2.0 mg/mL MnFe₂O₄-CS. The use of MnFe₂O₄-CS to stimulate carotenoid yeast production and the magnetic separation of biomass are promising nanobiotechnological alternatives. Magnetic cell immobilization is a perspective technique for obtaining cell metabolites.

This research investigated the physicochemical properties and biological activities of green-synthesized copper oxide nanoparticles (CuO NPs) via Moringa peregrina extract, graphene oxide (GO), and their composite (CuO-GO). SEM revealed the morphology and structure, indicating polygonal CuO NPs, thin wrinkled sheets of GO, and a combination of CuO NPs and GO in the nanocomposite. EDS confirmed the elemental composition and distribution. XRD analysis confirmed the crystalline monoclinic structure of CuO NPs and GO, as well as their composite, CuO-GO, with characteristic peaks. DLS analysis exhibited distinct size distributions, with CuO NPs showing the narrowest range. BET surface area analysis revealed mesoporous structures for all materials, with the nanocomposite showing enhanced surface area and pore volume. Anticancer assays on MCF-7 and normal NIH/3T3 cells demonstrated CuO-GO's superior cytotoxicity against cancer cells, with minimal effects on normal cells, suggesting selective cytotoxicity. Moreover, antibacterial assays against Pseudomonas aeruginosa and Staphylococcus aureus indicated CuO-GO's potent inhibitory activity. The composite's synergistic effects were evidenced by its lower minimum inhibitory concentration (MIC) compared to individual components. In conclusion, this study elucidated the promising biomedical applications of CuO NPs, GO, and their nanocomposite, particularly in cancer treatment and antibacterial therapies, showcasing their potential as multifunctional nanomaterials.

The septic tank is the most commonly used decentralized wastewater treatment systems for household wastewater treatment in on-site applications. The removal rate of various pollutants is lower in different septic tank configurations. The integration of a microbial electrolysis cells (MEC) into septic tank or biofilm-based reactors can be a green and sustainable technology for household wastewater treatment and energy production. In this study, a 50-L septic tank was converted into a 50-L MEC coupled with biofilm-based reactor for simultaneous household wastewater treatment and hydrogen production. The biofilm-based reactor was integrated by an anaerobic packed-bed biofilm reactor (APBBR) and an aerobic moving bed biofilm reactor (aeMBBR). The MEC/APBBR/aeMBBR was evaluated at different organic loading rates (OLRs) by applying voltage of 0.7 and 1.0 V. Result showed that the increase of OLRs from 0.2 to 0.44 kg COD/m³ d did not affect organic matter removals. Nutrient and solids removal decreased with increasing OLR up to 0.44 kg COD/m³ d. Global removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), ammoniacal nitrogen (NH₄⁺), total phosphorus (TP) and total suspended solids (TSS) removal ranged from 81 to 84%, 84 to 85%, 53 to 68%, 88 to 98%, 11 to 30% and 76 to 88% respectively, was obtained in this study. The current density generated in the MEC from 0 to 0.41 A/m² contributed to an increase in hydrogen production and pollutants removal. The maximum volumetric hydrogen production rate obtained in the MEC was 0.007 L/L^.d (0.072 L/d). The integration of the MEC into biofilm-based reactors applying a voltage of 1.0 V generated different bioelectrochemical nitrogen and phosphorus transformations within the MEC, allowing a simultaneous denitrification-nitrification process with phosphorus removal.