Biochemical Engineering Journal最新文献

Enterobacter cloacae G, a novel denitrifying phosphorus-accumulating bacterial strain, was isolated from anaerobic sludge tank of a wastewater treatment plant used for pig farms. It was discovered that a pH of 7, a temperature of 30°C, an initial phosphorus concentration of 8 mg/L, and a C/N ratio of 10 were the strain's ideal growth conditions. To ensure the stability of strain G in wastewater treatment, strain G was immobilized by 5 % polyvinyl alcohol, 2 % sodium alginate, and 0.6 g of biochar and crosslinked for 9 h in 4 % calcium chloride saturated boric acid solution via an orthogonal test. After the immobilized microspheres were introduced into the sequencing batch reactor (SBR), the nitrate and phosphate removal rates achieved were 89.36 % and 65.53 %, respectively, with a hydraulic retention time (HRT) of 8 hours, a pH of 7.5, and a C/N ratio of 4.5. The immobilized microspheres containing strain G demonstrated potential for the treatment of nitrogen-rich and phosphorus-rich wastewater.

Biomethanation offers a promising route for the valorization of synthesis gas, yet significant challenges arise from the limited conversion of carbon monoxide (CO). This study investigated the adaptation of an anaerobic microbiome in a continuous trickle bed reactor (TBR) with CO as the sole carbon and energy source. We evaluated reactor performance and microbial community changes under different CO loading rates and gas retention times (GRT). Optimal performance was achieved at a CO loading rate of 5.16 Nm³ m⁻³ d⁻¹ and a GRT of 60.6 min, resulting in average production rates of 0.99 Nm³ m⁻³ d⁻¹ for CH₄ and 2.55 Nm⁻³ m⁻³ d⁻¹ for CO₂, with an 88 % CO conversion rate. Microbial analysis indicated that the community was dominated by the genus Methanothermobacter, known for its ability to utilize CO as a sole substrate, followed by a co-dominance of syntrophic acetate-oxidizing bacteria Syntrophaceticus. This syntrophic relationship between Methanothermobacter and Syntrophaceticus is expected to be crucial for the efficient CO conversion process. Additionally, the study proposes a two-reactor system for converting synthesis gas to grid-quality methane.

Laccases are versatile biocatalysts with interest for various industrial applications. This study reports the expression of Trametes versicolor laccase in Komagataella phaffii X33. The cultivation parameters (methanol and CuSO₄ concentration, and temperature) for recombinant laccase production were studied in an orbital shaker. Enhanced laccase production was achieved by adding 1 % (v/v) methanol daily, supplementing 0.1 mM CuSO₄ and incubating at 25 °C. Under these conditions, laccase production was scaled-up in a 4 L stirred tank bioreactor. Subsequently, laccase was concentrated and purified using a combined protocol of ultrafiltration and acetone precipitation, achieving a purification factor of 3.02. The laccase produced exhibited robust stability within a pH range from 4.0 to 8.0 and thermal stability up to 30 °C. Michaelis Menten kinetic revealed Michaelis constant (K_M) and maximum rate of reaction (V_max) values of 44.5 µM and 110.9 µM/min, respectively. Finally, laccase was employed as a biocatalyst to assist the polymerization of dopamine to polydopamine, allowing the one-step coating of cellulose filter paper, as confirmed by diffuse reflectance spectroscopy (UV-Vis DRS) and scanning electron microscopy (SEM). This work represents an advance in the field of laccase production in both orbital shaker and bioreactor, while demonstrating, for the first time, the laccase-assisted polymerization of dopamine for the coating of filter paper with polydopamine.

The primary challenge in utilizing palm kernel meal (PKM, an agricultural by-product) as non-ruminant livestock feed is its high fibre content, predominantly in the form of mannan. Microbial fermentation offers an economically favourable alternative to enzyme supplementation for breaking down fibre in lignocellulosic biomass. In a recent study, our group isolated a B. subtilis strain F6 with a fast response time for mannanase production upon exposure to PKM. This work focuses on improving the mannanase production of the B. subtilis strain to achieve greater fibre hydrolysis of PKM without extending fermentation time. Mannanase GmuG, sourced from B. subtilis F6 and verified for its hydrolytic activity on PKM fibre, was homologously expressed using a replicative plasmid (pBE-S). Enzyme production was systematically improved by optimizing various regulatory elements, including the promoter, ribosome binding site, and signal peptide. Consequently, the neutral detergent fibre content of PKM was substantially reduced by 36.4 % in 22 h of solid-state fermentation using the engineered strain. Lastly, the highest mannanase-producing strain was examined for scaled-up fermentation. The impacts of fermentation on fibre and protein contents, as well as the surface morphology of PKM, were analysed. The outcomes of this study offer an efficient method for robust mannanase expression in B. subtilis and its potential application in the biotransformation of PKM and other mannan-rich bioresources for improved feed utilization.

Microalgae grabbed the attention worldwide because of their application in renewable energy with a number of environmental benefits such as carbon dioxide assimilation to produce biofuel. In this study, a kinetic model aiming to analyze algae growth and lipid production was developed. Biomass was divided into two parts, algae residual cell and lipid, to analyze their kinetics distinctively and to find out the inside process mechanism. The model was calibrated and validated with different experimental datasets, varying carbon sources, and phosphate concentrations. The capability of the model to predict the dynamics of algal culture over a broad range of growth conditions was investigated. The presence of acetate reduced the bicarbonate uptake for algal growth and growth on organic carbon was higher compared to that of carbon dioxide. The presence of ammonium showed a very strong inhibition effect on algae and lipid production rate but enhanced lipid content. Phosphate caused both limitation and inhibition effects on algae growth and lipid production rate. The maximum growth was found at 12 mg/L PO₄^3- concentration and 3.10 mg/L NO₃^--N concentration. Lipid content was enhanced by limiting phosphate. Overall, the developed model allows optimizing of nutrient concentrations and operating conditions specifically to enhance lipid productivity.

Antibiotics like Sulfamethoxazole (SMX) pose a significant threat to public health and environmental well-being. To address this issue, effective strategies are being developed to remove antibiotics from the environment. This study investigates the degradation of SMX with a focus on elucidating the mechanism by which extracellular electron transfer (EET) enhances the efficient degradation of the antibiotic. The results show that SMX was significantly degraded (97 %) by Shewanella oneidensis MR-1 after 120 hours in the presence of a bioelectrochemical system (BES) at a concentration of 1 mg L⁻¹, compared to the absence of BES (69 %) at the same concentration and time. BES was observed to simultaneously remove pollutants like SMX while generating electricity at this concentration. Proteomic analysis was further employed to clarify the mechanism behind this process. Three key SMX-degrading proteins; S-ribosylhomocysteine lyase (luxS), Deoxyribose-phosphate aldolase (deoC), and Amidohydrolase which mainly participated in C-S cleavage, S-N hydrolysis and isoxazole ring cleavage were identified. The study demonstrates that S. oneidensis MR-1 can promote the generation of Nicotinamide Adenine Dinucleotide and Adenosine Triphosphate and facilitate electron transfer to enhance the efficient degradation of SMX. The findings of this study provide new insights into the correlation mechanism between SMX degradation and EET, ultimately contributing to innovative solutions for environmental remediation.

Outdoor cultivation using natural sunlight efficiently produces valuable microalgal products, such as proteins, lipids, carbohydrates, and antioxidants but photoinhibition from intense sunlight must be minimized. This study explores the effect of varying simulated outdoor light intensity on Limnospira fusiformis growth and biochemical composition. Four light scenarios were tested to simulate varying outdoor light conditions: full sunlight (2000 µmol m⁻²s⁻¹), greenhouse (1700 µmol m⁻²s⁻¹), mid-day shade in a greenhouse (1400 µmol m⁻²s⁻¹), and whole-time shade in a greenhouse (1400 µmol m⁻²s⁻¹). Whole-time shade yielded the highest last-day dry weight (2.10 g L⁻¹), protein content (63.10 % ash-free dry weight), phycocyanin productivity (0.11 g L⁻¹d⁻¹), and lowest ash accumulation (11.00 %). High light intensity led to substantial carbohydrate accumulation, while protein synthesis and cell growth declined. This study is the first to report the correlation between high light-induced morphological changes with both protein and phycocyanin levels. Shading techniques enhanced biomass production and composition in Limnospira fusiformis. The observed improvements in protein content and phycocyanin productivity under specific light conditions demonstrate the potential for optimizing outdoor cultivation of indigenous microalgal strains, contributing to more efficient and sustainable production methods for industrial applications.

To explore the effects and mechanisms of long-lasting degradation of long-chain alkanes (C₂₅-C₃₀) in petroleum-contaminated soil, a solid iron catalyst prepared by adding different proportions of (5 % and 15 % (w/w)) chitosan (CS) was used for Fenton pre-oxidation experiment. Bioremediation experiments were performed for 100 days after pre-oxidation. The results indicated that the degradation for long-chain alkanes and Total Petroleum Hydrocarbons (TPH) were 76.95 % and 76.89 %, respectively. Furthermore, long-lasting degradation of long-chain alkanes was achieved by activating Bacillus-like microbes. In each biodegradation cycle, the long-chain alkanes degradation in the active control group increased by 77.39 mg/kg, 76.74 mg/kg, 36.88 mg/kg, and 76.51 mg/kg compared to the previous cycle. Besides, the half-life of long-chain alkanes was 131 days shorter in the active control group than in the inactive control group. Higher microbial enzyme activity for degrading long-chain alkanes was observed after Fenton pre-oxidation because the expression of alkane metabolism genes was activated by the high consumption of dissolved organic carbon. Finally, the dominant bacterial genera in the active control group shifted predominantly to Paenibacillus (13.26 %), Acinetobacter (8.02 %), and Microbacterium (17.64 %). Therefore, this study possesses significant engineering application value.

The inability of traditional pre-clinical cell culture and animal models to accurately replicate human diseases and drug toxicities leads to a significant halt in the advancement of effective treatment strategies, in addition to financial losses. This, combined with the rise in ethical concerns about animal welfare, highlights the need for alternative and more realistic representations of human physiology. Microfluidics-based multiorgan microphysiological systems present a promising avenue for studying human body homeostasis, and have the potential to revolutionize translational research by creating new opportunities to comprehend systemic diseases and develop personalized medicine. In this review, we describe important design and operational considerations for engineering microfluidic devices mimicking tissue/organ “cross-talk” for in vitro drug disposition and safety assessments, as well as in disease modeling. We conducted a meticulous analysis of relevant articles and calculated crucial parameters, like the Reynolds number and shear stress, to compare the operational characteristics of different microfluidic devices. Additionally, we provide the reader with perspectives on the current limitations, insights to address the pending issues, and describe future opportunities of these technologies in the clinical setting.

Genetic codon expansion has the potential to introduce a variety of unnatural amino acids to specific sites within target proteins. In this study, genetic codon expansion was employed to regulate the enzyme expression in metabolic pathways. Firstly, a purple protein from Actinia tenebrosa was selected as the candidate to be engineered. Bringing in UAG stop codon caused premature termination of translation, while expressing orthogonal aminoacyl-tRNA synthetase and tRNA from Methanococcus jannaschii restored translation at UAG site. However, leakage expression was observed without addition of unnatural amino acids, still it can be decreased by increasing numbers of UAG mutations. Subsequently, poly(lactate-co-3-hydroxyburyrate) [P(LA-3HB)] biosynthesis pathway was constructed in Escherichia coli, and propionyl-CoA transferase was mutated to harboring one or two more stop codons. With genetic codon expansion tools, the function of propionyl-CoA transferase was restored, promoting cells to synthesize P(LA-3HB) copolymer. Moreover, the lactate monomer content was regulated ranging from 0 to 33.42 mol% by altering the addition time of inducers. Finally, the strain accumulated 27.09 g/L P(25.1 mol% LA-3HB) in 5-L bioreactor cultivation. This is the first report on metabolic engineering of polyhydroxyalkanoate biosynthesis through genetic codon expansion and would provide helpful strategies to achieve dynamic regulation of multiple metabolic pathways.