Honghua Jia's research while affiliated with Nanjing Tech University and other places

BACKGROUND Biogenic metal nanoparticle‐modified electrodes have a promising prospect for improving the efficiency of microbial fuel cells (MFCs) for hexavalent chromium (Cr(VI))‐containing wastewater treatment. In this study, a graphene (GO) electrode was modified with chemical gold nanoparticles (ChemAu) and biogenic gold nanoparticles (BioAu), respectively, and the two modified electrodes were then used as MFC biocathode electrodes to treat Cr(VI)‐containing wastewater. RESULTS The results demonstrated that the BioAu/GO biocathode‐based MFC obtained the highest power density (95.78 ± 1.11 mW m⁻²) and Cr(VI) removal rate (2.17 ± 0.51 mg L⁻¹ h), which were 13.19 and 1.03 times higher than those of the graphite paper biocathode‐based MFC, respectively. The Cr(VI) removal efficiency of the BioAu/GO biocathode‐based MFC under close‐circuit condition reached 87.61 ± 0.19%, which was 3.74 times higher than that recorded under open‐circuit conditions, indicating the critical role of the bioelectrochemical reduction reaction mediated by the BioAu/GO biocathode on Cr(VI) removal. CONCLUSION The BioAu/GO electrode first confirmed its superior performance to the ChemAu/GO electrode in Cr(VI)‐reducing MFCs due to its excellent material properties. This study provides a technical reference for the exploration of efficient bioelectrode materials based on biogenic metal nanoparticles for MFCs to treat recalcitrant pollutant‐containing wastewater. © 2024 Society of Chemical Industry (SCI).

Identification of sucrose synthase from Micractinium conductrix to favor biocatalytic glycosylation. Sucrose synthase (SuSy, EC 2.4.1.13) is a unique glycosyltransferase (GT) for developing cost-effective glycosylation processes. Up to now, some SuSys derived from plants and bacteria have been used to recycle uridine 5-diphosphate glucose in the reactions catalyzed by Leloir GTs. In this study, after sequence mining and experimental verification, a SuSy from Micractinium conductrix (McSuSy), a single-cell green alga, was overexpressed in Escherichia coli, and its enzymatic properties were characterized. In the direction of sucrose cleavage, the specific activity of the recombinant McSuSy is 9.39 U/mg at 37 • C and pH 7.0, and the optimum temperature and pH were 60 • C and pH 7.0, respectively. Its nucleotide preference for uridine 5-diphosphate (UDP) was similar to plant SuSys, and the enzyme activity remained relatively high when the DMSO concentration below 25%. The mutation of the predicted N-terminal phosphorylation site (S31D) significantly stimulated the activity of McSuSy. When the mutant S31D of McSuSy was applied by coupling the engineered Stevia glycosyltransferase UGT76G1 in a one-pot two-enzyme reaction at 10% DMSO, 50 g/L rebaudioside E was transformed into 51.06 g/L rebaudioside M in 57 h by means of batch feeding, with a yield of 76.48%. This work may reveal the lower eukaryotes as a promising resource for SuSys of industrial interest.

Bioelectrochemical systems (BESs) are an emerging technology for wastewater treatment and resource recovery. These systems facilitate electron transfer between microorganisms and electrodes, enabling their application in various fields, such as electricity production, bioremediation, biosensors, and biocatalysis. However, electrode biofilms, which play a critical role in BESs, face several challenges (e.g., a long acclimation period, low attached biomass, high electron transfer resistance, and poor tolerance and stability) that limit the development of this technology. Quorum sensing (QS) is a communication method among microorganisms that can enhance the performance of BESs by regulating electrode biofilms. QS regulation can positively impact electrode biofilms by enhancing extracellular electron transfer (EET), biofilm formation, cellular activity, the secretion of extracellular polymeric substances (EPS), and the construction of microbial community. In this paper, the characteristics of anode electrogenic biofilms and cathode electrotrophic biofilms in BESs, EET mechanisms, and the main factors affecting biofilm formation were summarized. Additionally, QS regulation mechanisms for biofilm formation, strategies for enhancing and inhibiting QS, and the application of QS regulation for electrode biofilms in BESs were systematically reviewed and discussed. This paper provides valuable background information and insights for future research and development of BES platforms based on QS regulation of electrode biofilms.

Microbial fuel cells (MFCs) have been considered a promising technology for Cr6+ removal, but they are limited by Cr6+-reducing biocathodes with low extracellular electron transfer (EET) and poor microbial activity. In this study, three kinds of nano-FeS hybridized electrode biofilms, obtained through synchronous biosynthesis (Sy-FeS), sequential biosynthesis (Se-FeS) and cathode biosynthesis (Ca-FeS), were applied as biocathodes for Cr6+ removal in MFCs. The Ca-FeS biocathode exhibited the best performance due to the superior properties of biogenic nano-FeS (e.g., more synthetic amount, smaller particle size, better dispersion). The MFC with the Ca-FeS biocathode achieved the highest power density (42.08 ± 1.42 mW/m2) and Cr6+ removal efficiency (99.18 ± 0.1 %), which were 1.42 and 2.08 times as high as those of the MFC with the normal biocathode, respectively. The synergistic effects of nano-FeS and microorganisms enhanced the bioelectrochemical reduction of Cr6+, first realizing deep reduction of Cr6+ to Cr0 in biocathode MFCs. This significantly alleviated the cathode passivation caused by Cr3+ deposition. In addition, the hybridized nano-FeS as "armor" layers protected the microbes from toxic attack by Cr6+, improving the biofilm physiological activity and extracellular polymeric substances (EPS) secretion. The hybridized nano-FeS as "electron bridges" facilitated the microbial community to form a balanced, stable and syntrophic ecological structure. This study proposes a novel strategy through the cathode in-situ biosynthesis of nanomaterials to fabricate hybridized electrode biofilms with enhanced EET and microbial activity for toxic pollutant treatment in bioelectrochemical systems.

Quercetin-3,4'-O-diglucoside (Q3,4'G), among the major dietary flavonoids, is superior to quercetin aglycone or quercetin monoglucoside in solubility. However, its low content in nature makes it hard to be prepared in large quantities by traditional extraction methods. In the present study, the F378S mutant of UGT78D2 (78D2_F378S) derived from Arabidopsis thaliana with improved regioselectivity and the V371A mutant of UGT73G1 (73G1_V371A) derived from Allium cepa were adopted to realize a two-step continuous glycosylation of quercetin to produce Q3,4'G. The mutation S31D was introduced to the sucrose synthase from Micractinium conductrix with enhanced activity, which was responsible for regenerating UDP-glucose by coupling with 78D2_F378S and 73G1_V371A. Using the aforementioned enzymes, prepared from the three-enzyme co-expression strain, 4.4 ± 0.03 g/L (7.0 ± 0.05 mM, yield 21.2%) Q3,4'G was produced from 10 g/L quercetin after reaction for 24 h at 45 °C.

Biocathode microbial fuel cells (MFCs) show promise for Cr(vi)-contaminated wastewater treatment. However, biocathode deactivation and passivation caused by highly toxic Cr(vi) and nonconductive Cr(iii) deposition limit the development of this technology. A nano-FeS hybridized electrode biofilm was fabricated by simultaneously feeding Fe and S sources into the MFC anode. This bioanode was then reversed as the biocathode to treat Cr(vi)-containing wastewater in a MFC. The MFC obtained the highest power density (40.75 ± 0.73 mW m-2) and Cr(vi) removal rate (3.99 ± 0.08 mg L-1 h-1), which were 1.31 and 2.00 times those of the control, respectively. The MFC also maintained high stability for Cr(vi) removal in three consecutive cycles. These improvements were due to synergistic effects of nano-FeS with excellent properties and microorganisms in the biocathode. The mechanisms were: (1) the accelerated electron transfer mediated by nano-FeS 'electron bridges' strengthened bioelectrochemical reactions, firstly realizing deep reduction of Cr(vi) to Cr(0) and thus effectively alleviating cathode passivation; (2) nano-FeS as 'armor' layers improved cellular viability and extracellular polymeric substance secretion; (3) the biofilm selectively enriched a diversity of bifunctional bacteria for electrochemical activity and Cr(vi) removal. This study provides a new strategy to obtain electrode biofilms for sustainable treatment of heavy metal wastewater.

ω-Transaminases (ω-TAs) are widely available for the production of chiral amines and unnatural amino acids. Herein, a rapid spectrophotometric method was developed for screening ω-TAs based on the colored products that can be generated from transamination reactions between aliphatic α-diketones and amino donors catalyzed by ω-TAs. The possible mechanism of the formation of the colored product was investigated according to LC-Q-TOF–MS analysis. Among seven diketones, 2,3-butanedione was selected as the most suitable amino acceptor for colorimetric screening of ω-TAs with high efficiency, high sensitivity, and low background interference. Meanwhile, the absorbance of the colored product generated by 2,3-butanedione catalyzed by ω-TAs in this method was linearly correlated with the results by HPLC analysis. This method was also confirmed to effectively screen ω-TA mutants with high activity towards isopropylamine.Graphical Abstract

Based on the demand of enterprise talents and the characteristics of manufacturing process management in biotechnology, in order to make the students acquire the ability to solve complex engineering problems in the production process, we developed a "Comprehensive Biotechnology Experiment" course, where two-step enzymatic production of l-aspartate and l-alanine were the key processes. In this course, we drew lessons from the site management of the production enterprise, performed the experimental operation mode of four shifts and three operations. The content of this course includes principles, methods and experimental techniques of several core curricula and the site management mode of enterprises. As to the evaluation, the summary of the experimental staff's handover records and the content of teamwork were examined and scored. Through teaching practice and continuous improvement, we developed a complete experimental teaching process and assessment mechanism. Overall, the Comprehensive Biotechnology Experiment course achieved good teaching effect, which may serve as a reference to promote the development of experimental teaching of biotechnology.

Sucrose synthase (SuSy, EC 2.4.1.13) is a unique glycosyltransferase (GT) for developing cost-effective glycosylation processes. Up to now, some SuSys derived from plants and bacteria have been used to recycle uridine 5’-diphosphate glucose in the reactions catalyzed by Leloir GTs. In this study, after sequence mining and experimental verification, a SuSy from Micractinium conductrix (McSuSy), a single-cell green alga, was identified. In the direction of sucrose cleavage, the optimum temperature and pH of the recombinant McSuSy were 60 °C and pH 7.0. The mutations of the predicted N-terminal phosphorylation site (S31D) and the QN motif (K684T and N685D) significantly stimulated the activity of McSuSy. When the mutant S31D/684T/685D of McSuSy, with the highest activity, was applied by coupling the engineered yeast glycosyltransferase UGT51 in a one-pot two-enzyme reaction, 8 mM protopanaxadiol was transformed into 6.02 mM (3.75 g/L) ginsenoside Rh2 within 3 h at 37 °C. The yield was comparable to the control reaction of AtSuSy1 from Arabidopsis thaliana. This work reveals the lower eukaryotes as a promising resource for SuSys of industrial interest.