Biochemical Engineering Journal最新文献

Bacillus velezensis P#02 simultaneously produced surfactin and poly–γ–glutamic acid (γ–PGA). Among the different culture media studied, the one containing corn steep liquor (100 mL/L), glucose (10 g/L), and glutamic acid (10 g/L) as sole ingredients (CSL–G–Glut(10)) offered the best results regarding biosurfactant and biopolymer production. Although biosurfactant production occurred both under shaking and static conditions, significant biopolymer production occurred only in static cultures. Using the culture medium CSL–G–Glut(10), 910 ± 20 mg surfactin/L and 9.8 ± 0.2 g γ–PGA/L were produced. Surfactin was synthetized as a mixture of five different homologues (fatty acid chains ranging between C₁₂ and C₁₆), being the most abundant C₁₄– and C₁₅–surfactin. Surfactin reduced the surface tension up to 29 mN/m, with a critical micelle concentration of 52 mg/L, and exhibited a significant emulsifying activity. B. velezensis P#02 γ–PGA, which molecular weight was around 229 kDa, displayed a non–Newtonian shear–thinning profile, achieving apparent viscosity values around 3800 mPa s in aqueous solution, with a predominant viscous behavior. Accordingly, B. velezensis P#02 is a promising strain for the simultaneous production of γ–PGA and surfactin using the waste stream corn steep liquor.

Aromatic amines, the common organic metabolites of chemical raw materials and herbicides, has attracted wide attention due to its difficult degradation and carcinogenic risk. This study aims to use microbial co-metabolism technology to efficiently degrade p-chloroaniline (PCA), which is a highly toxic aromatic amine. From the perspective of enzyme substrate specificity, a system for efficient degradation of PCA using aniline as a co-substrate was constructed. The degradation conditions were optimized by response surface methodology, and the degradation efficiency of PCA was 81.12 % (50 mg/L). Further, the co-metabolism mechanism was clarified by multiple methods. Enzyme activity assay preliminarily showed that aniline induced catechol 2,3-dioxygenase activity. Then the intermediates of PCA and aniline degradation was identified and two possible PCA degradation pathways were proposed. Transcriptomic analyzed the molecular mechanism of aniline-enhanced PCA degradation: Nitrogen utilization efficiency was accelerated by up-regulation of nitrogen metabolism-related genes. Several oxidoreductases including catechol 2,3-dioxygenase were significantly up-regulated. TCA cycle and ATP synthesis were accelerated, facilitating cell metabolism and energy supply. The work contributes a worthy theory for the remediation of PCA-aniline co-contaminated sites.

Pyruvate, a pivotal metabolite in the glycolytic pathway, typically confronts substantial barriers to its natural accumulation within microbial cells. This study successfully facilitated the natural accumulation of pyruvate in Actinobacillus succinogenes 130Z by fine-tuning the oxidation-reduction potential (ORP) in the fermentation milieu. A mechanistic exploration revealed that the accumulation of pyruvate was optimized when ORP conditions favorably modulated pyruvate kinase activity and concurrently suppressed succinate dehydrogenase activity. By integrating the influence of metal ions on enzymatic functions with an innovative aluminum ion-mediated ORP control strategy, we achieved a pyruvate yield of 27.54 g/L over 20 hours, which constitutes an 89.54 % increase compared to the baseline. Additionally, the production rate of pyruvate reached 1.38 g/L·h. This investigation not only elucidates the metabolic underpinnings that facilitate the natural enrichment of glycolytic intermediates in Actinobacillus succinogenes 130Z but also lays a robust theoretical foundation for the industrial-scale fermentation of pyruvate. Moreover, the capability to efficiently and rapidly concentrate essential platform metabolites within the glycolytic pathway is of paramount significance, potentially propelling forward the research and synthesis of various downstream metabolic products.

To improve heat tolerance and biomass yield of microalgae cells cultivated with flue gas in power plants in South China in summer, Scenedesmus quadricauda cells were cultivated at various temperatures to regulate functional metabolic pathways. The microalgae biomass production was 26 % higher at 35°C than at 25°C. The expression of photosynthesis-related proteins was up-regulated by 14.3 %, enhancing electron transfer efficiency and oxygen release rate at photosynthetic carbon fixation. Furthermore, microalgal cells absorbed more sulfur to enhance sulfur metabolism. The extracellular polymeric substances (EPS) content increased by 2.71-fold, improving the survival activity under high-temperature stress. The up-regulation of lysosomes and hydrogenases promoted the cellular removal of metabolic wastes and damaged organelles and improved the antioxidant defense capacity. Moreover, the microalgal cells maintained normal growth at 40°C through a self-regulatory mechanism. In contrast, the photosynthetic carbon fixation of microalgae cells was strongly inhibited at 42°C. This study revealed the adaptive mechanism of cellular carbon fixation in microalgae at high temperatures, which improved the high-temperature tolerance and biomass production of microalgae.

Simultaneous nitrification denitrification and phosphorus removal (SNDPR) is an elegant process that can uptake influent carbon and effectively remove nitrogen and phosphorus from wastewater. However, meeting the increasingly stringent effluent discharge standards requires a more stable performance. This study aimed to analyze the nitrogen and phosphorus removal performance and microbial community shifts of SNDPR system under different levels of dissolved oxygen (DO) in a sequencing batch reactor (SBR). Results showed that maintaining DO levels at 0.4 ± 0.2 mg/L significantly enhanced nutrient removal efficiencies, with an average nitrogen and phosphorus removal rate of 86.28 ± 7.42 % and 92.40 ± 10.48 %, respectively. The research also identified Saccharimonadales sp. as a crucial microbial genus, with its relative abundance increasing from 1.38 % to 28.16 % under optimized conditions. These findings demonstrate that optimizing microbial interactions and DO levels can lead to substantial improvements in wastewater treatment performance, making the process economically viable. This discovery provides a potential pathway for optimizing wastewater treatment processes, leading to the improvement of nutrient removal efficiency, cost savings, and enhancement of environmental sustainability.

Food waste generation is an unavoidable issue due to the increase in the human population and economic growth worldwide. Therefore, it is crucial to explore various eco-friendly and sustainable waste management practices to reduce these environmental impacts while creating value-added products derived from these food waste resources. The cultivation of microalgae can contribute to the global carbon neutrality process and help reduce the emission of greenhouse gases into the environment. However, several concerns such as food safety, quality, social acceptability, and the perception of using food waste to cultivate microalgae remain uncertain in the current food waste management. This review provides a comprehensive assessment of the biochemical mechanisms involved in the metabolization process of microalgae, assimilating organic compounds derived from food waste sources and emphasizing the importance of understanding these complex processes. This review also explores the intricate relationships among the variations in food waste composition, hydrolysis processes, and nutrient bio-accessibility during cultivation of microalgae. Furthermore, we conducted a thorough evaluation of techno-economic analyses and life cycle assessments from various literature sources, highlighting several key elements such as the economic feasibility and environmental impacts of producing microalgae biomass from food waste. Finally, this review summarizes the future outlook and way forward in upcycling food waste with microalgae biotechnology by providing several recommendations for improvement.

L-Asparaginase (ASNase) is a versatile enzyme that converts L-asparagine into ammonia and aspartic acid. This enzyme has applications in the food industry and health sector. However, high purity ASNase is required, resulting in high production costs. Therefore, in this work, two supported ionic liquids (SILs), specifically silica modified with dimethylbutylpropylammonium chloride ([Si][N₃₁₁₄]Cl) or triethylpropylammonium chloride ([Si][N₃₂₂₂]Cl), were investigated as alternative adsorption materials to purify ASNase. Different conditions were evaluated to improve enzyme purity, including total protein content in the cell extract, contact time, and SIL/cell extract ratio (w/v). Under optimal conditions using [Si][N₃₁₁₄]Cl, a maximum ASNase purification of 6.1-fold is achieved in a single step, resulting from the preferential attachment of other proteins on [Si][N₃₁₁₄]Cl SIL. According to the results, hydrophobic interactions rule the selective adsorption of protein impurities from the cell extract by the SIL, thereby increasing the ASNase purification levels. This approach offers a significant advantage, not requiring the desorption and elution of the target enzyme, while envisioning the application of SILs in a flow-through elution approach. The protonation state of protein surface was calculated by computational analysis, revealing that positively charged amino acids such as arginine and lysine block the effective binding of the enzyme to the SILs. Overall, if properly designed, SILs are promising alternative supports for the downstream processing of ASNase from cell extracts.

CO₂ sequestration is important for reducing greenhouse effects. Carbonic anhydrase (CA) from bacteria has a promising role because it can be modified by genetic techniques and bioengineering. In this study, the CA from B. cereus GLRT202 (Bc-CA) was genetically engineered and anchored on the surface of E. coli by using the N-domain of the ice nucleation protein from P. syringae (INPN). Both surface-displayed and cytosolic Bc-CA yielded high expression levels of CA when induced with 0.5 mM IPTG. It exhibited no adverse influence on the host cell growth. Additionally, surface-displayed Bc-CA enhanced its stability and specificity compared to cytosolic expressed Bc-CA. The CA activity of whole-cell surface-displayed cells was 1.66-fold higher (5.19 U/mL) than that of the cytosolic form. Besides the advantages of higher activity, the whole-cell displaying CA was comparatively stable, with better storage (at 4 ℃) and resting culture stability (at 37 ℃). The whole-cell biocatalyst induced the calcite precipitation, which indicated that the cell facilitated the CO₂ capture. XRD, FTIR, and FESEM characterized calcite precipitates thus obtained. This study demonstrates that Bc-CA can be correctly expressed on the E. coli surface through fusion with the INPN. This leads to an effective whole-cell biocatalyst with enhanced stability and specificity of the enzyme for efficient CO₂ capture applications.

Harmful algal blooms (HABs) have posed a significant threat to human society and the ecological environment. In particular, the outbreak of Phaeocystis globosa (P. globosa) bloom could affect coasts nuclear power safety. Unfortunately, current ecological monitoring tools fail to dynamically detect the densities of solitary cells from P. globosa in the pre-outbreak phases, thus affecting early interventions. In the study, an effective electrochemical DNA biosensor was developed to serve the rapid and effective detection of P. globosa DNA through a specific DNA probe strategy. Especially, its good specificity and lower limit of detection (LOD, 17 pg/μL or 1063 cells/L) met the monitoring requirement of solitary-cell population change of P. globosa before the cyst formation (threshold: 1.0 × 10⁷ cells/L), which is the key step in the algal bloom outbreaks and influences the outbreak cycle and scale. Furthermore, the accuracy of this electrochemical biosensor for the quantitative detection of solitary-cell P. globosa was confirmed by using the classical microscopic examination techniques (r = 0.981, P < 0.001). Moreover, its applicability was also validated by actual sample testing (r = 0.996, P < 0.001). Therefore, the novel technology offers great potential to improve dynamic detection and early warning of P. globosa bloom.

This study is aiming to evaluate the optimization potential of anaerobic digestion systems for the treatment of complex agro-industrial wastes at an industrial scale. In previous work, the performance of a 20 L pilot-scale Plug Flow Reactor (PFR) that was able to operate at Organic Loading Rates (OLRs) of up to 25 kg Chemical Oxygen Demand (COD) m⁻³ d⁻¹, was demonstrated. This concept was then successfully transferred in a semi-industrial scale PFR of a volume equal to 50 m³, and the optimal operational parameters were evaluated. The construction of a full industrial scale facility followed, utilizing initially a 380 m³ PFR. Since PFR systems in practice do not behave ideally, due to short Length to Diameter ratio (L/D) and/or higher axial dispersion, the ideal PFR behavior was compared with real data of the non-ideal industrial-scale system; a performance reduction of 25–30 % was detected. However, the disadvantage of the non-ideal behavior of PFRs can be overcome by the cascaded arrangement of two such reactors (2 × 380 m³ PFRs), leading to a total volume reduction of 35 %, as depicted by experimentation on the industrial scale cascaded PFRs. The optimal design parameters for the PFRs are provided.