Bioprocess and Biosystems Engineering最新文献

Although microbial immobilization has been widely applied in wastewater treatment, the functional differences between suspended sludge and carrier-attached biofilms remain poorly understood. In this study, we investigated the microbial community structure and potential metabolic differences between suspended sludge (MIS) and polyurethane foam (PUF)-attached biofilms (MIC) in an immobilized biochemical tank (MI) from a chemical fiber plant. Compared to the conventional activated sludge process (CAS), the MI demonstrated significantly enhanced removal efficiencies of 39.4% for COD and 83.3% for BOD. The richness, diversity and unique microorganisms of MIS were higher than those of MIC. The dominant genera in MIS were Aridibacter, Diaphorobacter, Nostocoida, Pirellulaceae, Mucilaginibacter, and Rhodanobacter, while the dominant genera in MIC were Mucilaginibacter, Aridibacter, Nostocoida, Gemmata, Meiothermus, and Mycobacterium. Although the major genera were consistent, their relative abundance varied. Metabolic pathway analysis indicated that MIS showed stronger contributions to the transport of organic pollutants, while their role in nitrogen removal in the wastewater was greater than that of attached microorganisms. In contrast, carbon removal primarily occurred on the MIC. Moreover, the intensity of stochastic processes in shaping bacterial communities was observed as CAS (R² = 0.427) > MIS (R² = 0.261) > MIC (R² = 0.26), suggesting that the carriers enhanced the exposure of microbial communities to deterministic processes. These findings offer concrete theoretical support for the engineering application of microbial immobilization technology in treating industrial wastewater by elucidating key mechanistic insights.

DAAO is applied as a potential catalyst in the biosynthesis of L-PPT. However, its low solubility expression constrains its broader industrial application. Herein, a novel DAAO derived from Cladophialophora carrionii (CcDAAO) was identified, which demonstrated superior catalytic performance toward D-Ala (specific activity: 106.38 ± 1.21 U/mg, K_m: 1.56 ± 0.06 mM), along with remarkable thermostability and broad substrate spectrum. Under optimal culture conditions, the soluble expression level of CcDAAO was enhanced through a co-expression strategy with molecular chaperones, and the enzyme activity increased by 36.3% compared with the initial level. Subsequently, CcDAAO was constructed as a fusion protein (CGD) with catalase from Geobacillus sp. CHB1 (GbCAT) and applied in a D-amino acid aminotransferase (DAAT)-mediated cascade system. In a 2 L reaction system, this cascade system achieved complete conversion (> 99%) of 1 M D,L-PPT within 8 h, exhibiting a yield of 11.26 g/L/h for PPO, which represents a significant improvement over existing reports. This study presents a promising practical approach for the industrial production of optically pure L-PPT.

Microbe-assisted synthesis of metallic nanoparticles (NPs) has carved a niche among different NP generation methods owing to its simplicity, non-toxicity, low energy requirements, and potential scalability. Microorganisms have ability to produce NPs both intracellularly and extracellularly due to the presence of enzymes, proteins, and other biomolecules that can act as reducing and capping agents. However, a complete mechanistic understanding of this biosynthesis remains elusive. Biosynthesis is influenced by a myriad of factors, such as pH, temperature, reactant concentrations, reaction time, and light. The physicochemical factors associated with the synthesis process affect the morphological, biological, and catalytic properties of the NPs produced. This review focuses on the current paradigm and gaps in our understanding of microbial production pathways and the effects of physicochemical factors on the synthesis and application of various types of metallic NPs. The surveyed literature clearly elucidated the effect of these factors on the size, shape, dispersity, surface properties, and the reaction kinetics. The variations in morphological and surface properties were found to affect the performance of NPs in different applications such as catalysis, antimicrobial, and anticancer activities. Understanding the mechanistic pathways and the influence of physicochemical factors on synthesis can be potentially beneficial for the production of NPs with controlled shapes and sizes, tailored for specific applications.

The main goal of this study was to evaluate the potential of four yeasts-Rhodotorula mucilaginosa CCT 7688, Sporidiobolus pararoseus CCT 7689, Pichia fermentans CCT 7677, and Phaffia rhodozyma NRRL Y-17268-to produce carotenoids using soybean molasses as the sole nutrient source. Initially, they were cultivated in the medium-containing soybean molasses (C1, 34.32 g L^-1) and compared to the standard medium Yeast Malt (YM). R. mucilaginosa showed similar performance in both media. S. pararoseus had better performance in soybean molasses than in YM, since biomass and carotenoid production was higher. On the other hand, P. fermentans showed higher growth in soybean molasses, but pigment production was lower. P. rhodozyma outperformed in soybean molasses, resulting in higher biomass production (7.21 g L⁻¹), total carotenoid production, expressed as β-carotene (129.49 µg g⁻¹ and 914.71 µg L⁻¹), and astaxanthin production (188.25 µg g⁻¹ and 1388.84 µg L⁻¹). In addition, the use of soybean molasses showed potential to reduce about 90% of culture medium costs, in the case of this strain, in comparison with YM. Thus, P. rhodozyma was selected for the assays at different soybean molasses concentrations: 100 (C2), 150 (C3), 200 (C4), and 250 (C5) g L⁻¹. The best results were observed at C3, which provided significant increase in biomass (15.73 g L⁻¹) and total carotenoids, expressed as β-carotene (2229.30 µg L⁻¹) and astaxanthin (3519.65 µg L⁻¹). Compared to the initial medium (C1), gains exceeded 150% in some parameters, demonstrating that soybean molasses is an efficient, low-cost cultivation substrate with high potential to enable yeasts to produce carotenoids.

Wheat straw is a renewable biomass with potential for bioethanol and biorefinery applications, offering potential value-added products such as enzymes and oligosaccharides. However, its complex lignocellulosic structure, costly pretreatment requirements, and formation of inhibitory compounds hinder its utilization. Moreover, commercial enzymes used in saccharification are expensive, highlighting the need for efficient in-house enzyme production. This study investigates the application of a biological pretreatment using Trametes versicolor as an eco-friendly and cost-effective method to enhance cellulose content in wheat straw. The pretreated biomass was analyzed via acid hydrolysis and employed as a substrate for cellulase production by Penicillium chrysogenum through solid-state fermentation (SSF). The liquid extract obtained after washing the biomass was evaluated for laccase and manganese peroxidase (MnP) activities. In addition, acid hydrolysis was performed to detect oligosaccharides. Biological pretreatment increased cellulose content from 36.24 ± 1.74 to 41.25 ± 1.65% and reduced lignin from 28.66 ± 1.08 to 21.12 ± 1.22%, confirming effective delignification. The pretreated straw supported cellulase production with activities of 2.66 ± 0.044 U/g (FPU), 20.77 ± 1.91 U/g (BGL), and 75.02 ± 2.48 U/g (CMC). Also, xylooligosaccharides reached 1.15 ± 0.06 g/L on day 21. These results demonstrate the potential of combining biological pretreatment and SSF as a sustainable approach to enhance enzyme yields and recover oligosaccharides for biorefinery applications.

Self-amplifying mRNA (SAM) shows promise for vaccines and gene therapy because of its self-replicating ability. However, current studies lack sufficient information for systematic parameter optimization and differentiation from conventional non-replicating mRNA (NRM). Therefore, the transfection efficiency of NRM and SAM platforms was evaluated by comparing delivery vectors and optimizing parameters for the SAM protocol. SAM and NRM showed similar transfection preferences, but their efficiencies differed. Optimized SAM transfection parameters were then established, including dose and incubation time. In this study, an in vitro multi-parameter delivery system for SAM was constructed, providing valuable insights into SAM transfection and its distinction from regular mRNA. This study contributes an experimental basis for the rational screening of nucleic acid drug carriers and the establishment of SAM multi-parameter evaluation criteria, and also lays an important foundation for optimizing low-dose immunization strategies and their clinical application translation.

As environmental pollution problems become increasingly severe, the treatment of persistent organic pollutants has emerged as a major challenge in the field of environmental protection. Laccase, as a green and efficient biocatalyst, demonstrates significant potential for application in environmental remediation due to its unique oxidation capabilities and broad substrate specificity. This study systematically investigated the optimization of conditions for laccase production by Coriolus versicolor, the impact of fed-batch feeding and co-cultivation with a second fungal strain on laccase secretion by C. versicolor, and the degradation performance of the produced laccase towards 2,4-dichlorophenol (2,4-DCP). The results showed that during submerged fermentation, the laccase activity of C. versicolor increased significantly over time, peaking on the 6th day, and then gradually declined due to nutrient depletion and metabolite accumulation. Optimization of wheat bran concentration (20 g/L) and initial pH value (5.0) facilitated laccase production. Additionally, fed-batch feeding during fermentation was beneficial for laccase secretion by C. versicolor. Co-cultivation with a filamentous fungus Penicillium significantly increased laccase production. On laccase-mediated degradation of 2,4-DCP, the optimal enzyme dosage (4.0 U/mL), substrate concentration (20 mg/L), and degradation time (60 h) were established. Addition of mediator 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (0.5 mmol/L) significantly improved degradation efficiency, achieving complete degradation of 2,4-DCP. HPLC analysis further verified the practical application of laccase in environmental remediation. This study provides technical support for the preparation of highly active laccase and its application in the remediation of organic pollutants through degradation.

There is significant interest in employing cyanobacteria for eco-friendly biofuel production, utilizing CO₂ and sunlight. Recent advancements highlight the advantages of pathway engineering in cyanobacteria in enhancing the yields of biobutanol from the engineered strains. Isobutanol has excellent potential as an alternative fuel and can be blended with gasoline in ratios reaching 100% for use in existing internal combustion engines (ICE). This research focuses on the genetic engineering of Synechocystis sp. PCC 6803 to create mutant strains impaired in PHB synthesis but can biosynthesize isobutanol through an incorporated 2-keto-acid pathway in their genome. The synthesis of isobutanol is achieved through the heterologous expression of α-ketoisovalerate decarboxylase (Kivd) and alcohol dehydrogenase (Yqhd), both driven by the strong, light-inducible psbA2 promoter. The PHB synthase mutant strain ECDM12, which produces isobutanol, showed a 3.8-fold higher titer than PHB-synthesizing strains under identical cultivation conditions. Indoor cultivation in a 2 L photobioreactor (PBR) under simulated diurnal light resulted in the highest titer of 687.6 mg L^-1 (11th day) and productivity of 64.1 mg L^-1 day^-1. Outdoor studies in PBR under natural sunlight resulted in a maximum titer of 398 mg L^-1 (15th day) and productivity of 33.7 mg L^-1 day^-1, marking the first photosynthetic isobutanol production under natural sunlight.

Membrane proteins (MPs) are essential for various cellular functions and therefore critical targets for the drug industry. However structural and functional studies of MPs are challenging due to the difficulty and cost of solubilization and purification. Effective solubilization typically requires the incorporation of MPs into detergent micelles. Despite that this is a common practice, it has the potential to destabilize MPs. Alternatively, detergent-free systems have emerged, and reconstitution of MPs in Amphipol (APol) is one of the common methods. Polystyrene beads are generally used for this purpose. We investigated and evaluated the effectiveness of polydivinylbenzene Purolite™ PuroSorb™ PAD600 beads for detergent removal in membrane protein solubilization. To accomplish this, the membrane protein FtsH, solubilized in either DDM or LMNG, was exchanged with varying concentrations of APol, and detergents were removed by Purolite™ PuroSorb™ PAD600 beads. The results demonstrate that Purolite™ PuroSorb™ PAD600 beads are effective for detergent removal when the mass ratio of the Membrane Protein:Amphipol (MP:APol) is increased up to 1:10. The usage of Purolite™ PuroSorb™ PAD600 beads supports biochemical applications for membrane protein isolation and purification studies.

Single-cell protein (SCP) produced by yeast using low-cost agricultural wastes shows great potential as an alternative protein source for animal and human nutrition. In this study, we developed an adaptive evolution method coupled with centrifugal fractionation and pH shifting to enhance SCP production by Trichosporon cutaneum from wheat straw. During the adaptive evolution, the culture pH was shifted from 5.0 to 7.0, which is more favorable for SCP accumulation of T. cutaneum. The finally obtained T. cutaneum CL160 exhibited a 109.2% increase in SCP content compared to the parental strain. The DCW and SCP titer of T. cutaneum CL160 reached 48.6 ± 1.5 g/L and 14.2 ± 1.1 g/L using wheat straw clarified hydrolysate by batch fermentation. Fed-batch fermentation using wheat straw-derived syrup further improved DCW and SCP titer to 124.2 g/L and 32.6 g/L. Further attempts were performed to prepare soluble yeast extract from lignocellulose-derived SCP by cell autolysis. This yeast extract served as an effective nitrogen source for lactic acid fermentation by Pediococcus acidilactici, achieving 83.2 ± 1.1 g/L lactic acid titer and 45 × 10⁹/mL CFU value, comparable to commercial yeast extract. This study demonstrates the conversion of waste lignocellulosic feedstocks into sustainable SCP and soluble yeast extract, presenting an innovative strategy for the valorization of non-food lignocellulosic feedstocks.