Bioprocess and Biosystems Engineering最新文献

Exopolysaccharides (EPS) are natural macromolecular carbohydrates with good functional activity and physiological activities, but their industrial application was limited by high production costs and unclear structure-function relationships. This study developed a circular economy strategy to produce EPS via microbial fermentation using two food processing wastes (cane molasses and soy sauce residue). After optimizing fermentation medium, the waste-based system achieved an EPS yield of 33.06 ± 0.54 g/L. Two heteropolysaccharides-EPS-2 and EPS-3 were successfully isolated and purified. Monosaccharide composition analysis revealed that EPS-2 primarily consisted of arabinose, glucose, and galactose in a ratio of 65.35:20.82:13.83. In contrast, EPS-3 exhibited a more complex profile containing rhamnose (33.54%), galactose (31.62%), fucose (17.93%), arabinose (13.47%), and glucose (3.44%). Notably, EPS-3 demonstrated higher antioxidant activity than EPS-2. This study successfully demonstrates an innovative waste-to-value conversion strategy that not only achieves high-value utilization of discarded resources but also establishes the fundamental theoretical framework for scalable production of renewable biopolymers.

Biological treatment of high-strength (above 500 mg/L NO₃^--N) nitrate wastewater is often limited by process instability, nitrite accumulation and nitrous oxide (N₂O) emissions. This study developed a synergistic biochar-bacteria hybrid system by coupling a non-N₂O-accumulating denitrifier (Citrobacter freundii XY-1) with biochar (BC550) derived from spent mushroom substrate. Pyrolyzed at 550 ℃, BC550 exhibited high electron transfer capacity and served as a multifunctional carrier, facilitating biofilm formation and enabling high-rate nitrate removal. In a continuous-flow biofilter treating 1200 mg/L NO₃^--N, the system maintained a nitrate removal efficiency exceeding 97.5% for over 100 days at a hydraulic retention time of 15 h and C/N ratio of 10, with effluent nitrite consistently below 3 mg/L. Microbial community analysis confirmed the stable dominance of the inoculated XY-1 strain (39.7%), demonstrating successful bioaugmentation and system resilience. This work presents a stable and environmentally friendly hybrid system for high-strength nitrate removal, achieved through the rational coupling of functional biochar with a specific beneficial microorganism to ensure high treatment efficiency and mitigate N₂O emission risk.

Low influent carbon-to-nitrogen (C/N) ratios often limit denitrification in municipal wastewater treatment systems. This study evaluated denitrification performance in a full-scale anaerobic-anoxic-oxic (AAO) process equipped with a 6 m-deep anoxic tank containing spherical fixed carriers. Sludge flocs and carrier-attached biofilms were sampled at depths of 1 m, 3 m and 5 m along the horizontal flow path. Denitrification kinetics were quantified using batch tests, and microbial community structures were analyzed by 16 S rRNA gene sequencing. Sludge flocs exhibited the highest denitrification rates at 1 m, whereas biofilms performed optimally at 3 m. Along the horizontal direction, sludge flocs near the influent and external carbon dosing site showed enhanced denitrification, while biofilms downstream of the propeller demonstrated improved denitrification. Elevated dissolved oxygen (DO) introduced by internal reflow reduced the effective utilization of the external carbon source. Nitrosomonas was more abundant in sludge flocs, whereas Thauera dominated denitrifying community and peaked at 3 m in biofilms. Based on the spatial distribution of denitrification kinetics and microbial communities, the conventional "pre and top" carbon dosing strategy was re-evaluated, and an optimized "post and top" dosing strategy was proposed. This strategy reduced chemical oxygen demand (COD) consumption per unit of total nitrogen (TN) removed by 16%, providing a practical approach to enhance denitrification efficiency and external carbon utilization in full-scale anoxic tanks.

Global economic burden due to plastic pollution is estimated to be over $3 trillion annually. Bioplastics derived from bacteria-synthesized biopolymers like polyhydroxyalkanoates (PHAs), are a remarkably versatile sustainable alternative. Research on optimal growth-conditions for microbial PHA-synthesis fed-on sustainable substrates, particularly by phototrophic-mixed-cultures (PMC) enriched with purple non-sulphur bacteria (PNSB) is essential. This study intends to understand the effect of nitrogen and phosphorus concentrations on PHA-production by PMC grown using fuel synthesis wastewater (FSW) (organic by-product of Fischer-Tropsch process) as substrate. Stoichiometric quantification and 16 S metagenomic sequencing followed by statistical and bioinformatic analysis were done. High PHA-production (65-82% of biomass) is observed to be induced by Low-Nitrogen conditions enriching Rhodopseudomonas, Paludibacter and Pleomorphomonas and a Low-Phosphorus condition enriching Rhodopseudomonas, Rhodoplanes and Lentimicrobium. Analysis of metabolic-potential revealed 16 enzymes (of 8 different PHA-synthesis-pathways) inherent within the genomes of bacteria enriched by these culture conditions. This study identifies optimal nitrogen and phosphorus concentrations and the corresponding microbial-composition of FSW substrate-grown PMC-system to maximize PHA-production in a laboratory-scale bioprocess.

Ginkgo biloba leaves contain many kinds of active ingredients, which can affect the metabolism of animals to a certain extent, thus promoting the growth performance and disease prevention and resistance of animals. After microbial fermentation, Ginkgo biloba leaves can better retain and release their active ingredients, and achieve full utilization of biomass, making them suitable as feed additives. In this study, we conducted an orthogonal optimization experiment with 7 factors and 3 levels using Ginkgo biloba leaves as the substrate, employing two probiotic strains Bacillus licheniformis and B. natto as the fermentation strains, respectively. The results indicated that the fermented leaves were enriched with probiotics and demonstrated enhanced levels of flavonoids, total amino acids, crude protein and aroma substances. Specifically, the flavonoid content increased by 16.7% and 10.6%, total amino acids by 17.22% and 31.05%, total protein by 43.83% and 58.74%, and protease activities reached 1307 U/g and 1510 U/g, for B. licheniformis and B. natto, respectively. Furthermore, supplementation with 0.3-0.6% (mass fraction) of the Ginkgo biloba leaf fermentation product in broiler diets significantly improved the feed efficiency of brolier chickens at 21-42 d and 1-42 day. Through biological solid-state fermentation and conversion, the biological activity, nutritional value, and palatability of Ginkgo biloba leaves were significantly enhanced. When used as a feed additive for Ginkgo biloba leaves, it promoted the development of thymus and spleen, improved the antioxidant capacity of broiler chickens, significantly increased the pH of breast muscle for 24 h, reduced shear force, and significantly reduced the level of cooking loss of breast muscle, thus expanding a new way for efficient and high-value utilization of Ginkgo biloba leaves.

This study investigated the effects of iron-based materials-microscale zero-valent iron (mZVI), nanoscale zero-valent iron (nZVI), and nanoscale magnetite (nano-Fe₃O₄, in two size ranges: 50[Formula: see text]100 nm and 14[Formula: see text]29 nm)-on the anaerobic digestion (AD) of thermally hydrolyzed sewage sludge (THSS). Batch experiments were conducted under mesophilic conditions with three dosages (5, 15, and 30 mg/g-TS) of each material. Methane production kinetics were analyzed using the modified Gompertz model. A sequential extraction procedure was used to assess the speciation of potentially toxic elements (PTEs), namely, Zn, Cu, Pb, Ni, and Cr, in the digestates. The results showed that both mZVI and nZVI enhanced cumulative CH₄ production more than either size of nano-Fe₃O₄. The highest cumulative CH₄ yields (223 mL/g-VS_added), approximately 9% higher than the control, were achieved at nZVI dosages of 5 and 15 mg/g-TS. Among iron-based materials, nZVI most effectively shortened the lag phase (1.6-fold decrease at 15 mg/g-TS), whereas both sizes of nano-Fe₃O₄ had minimal effect (maximum 1.06-fold decrease for the 50-100 nm Fe₃O₄ at 30 mg/g-TS). The addition of mZVI and nZVI increased the mobility of Zn, Cu, and Ni in the digested THSS samples, while both nano-Fe₃O₄ materials reduced mobility of all studied PTEs. Overall, the results indicate a trade-off between enhanced methane production and environmental risk; mZVI and nZVI improve AD but increase PTE mobility, whereas nano-Fe₃O₄ mitigates PTE mobility with little or no effect on CH₄ production.

Microalgae, such as Tetraselmis chuii, are potent sources of natural antioxidants, attributed to their adaptation to oxidative stress in harsh marine environments. This study aimed to investigate superoxide dismutase (SOD) production in T. chuii, a microalga recently approved as a novel food by the European Union. Although oxidative stress application was hypothesized to enhance SOD biosynthesis, direct stress exposure potentially compromises biomass accumulation, creating a trade-off between cell density and antioxidant production. Therefore, a two-stage cultivation strategy was employed: the first stage focused on optimizing biomass through medium enhancement until an adequate cell density was achieved in the stationary phase, followed by the controlled induction of oxidative stress to stimulate SOD overproduction without significantly impacting the established biomass. F medium, supplemented with NH₄Cl, was selected as the basal cultivation medium. Key components, such as NH₄Cl, NaH₂PO₄, CuSO₄, and MnCl_2, were optimized using Response Surface Methodology (RSM), increasing biomass from 416.67 mg/L to 564.44 mg/L and SOD activity from 1479.23 U/g to 2757.27 U/g. Various stressors, including trace heavy metals, oxidants, and salinity modulation, were applied to elevate SOD production further. CuSO₄, used as a stressor, proved most effective at 5.0 mg/L, increasing SOD activity to 5774.76 U/g compared to 2307.62 U/g in the control. To build microalgal tolerance towards copper-induced stress, an Adaptive laboratory evolution (ALE) experiment was conducted over 27 weeks, resulting in a post-ALE strain with a 61% increase in SOD activity. Overall, this study demonstrates the effectiveness of medium optimization, stress induction, and ALE in augmenting antioxidant production in microalgae.