A novel strategy to alleviate medium acidosis for simultaneously yielding more bacterial cellulose and electricity

Bacterial cellulose (BC), a fascinating and renewable polymer, can be applied widely in various bio-based materials. However, its synthesis is generally limited by medium acidosis. Herein, we demonstrated a built-in galvanic cell within the BC fermentation medium to alleviate the acidosis, by which BC yield was promoted by 191%, and simultaneously the yield of electrical power of 0.68 W to 8.10 W during the incubation.

Bacterial cellulose (BC), a fascinating and renewable polymer, can be applied widely in various bio-based materials.

Bacterial cellulose (BC) is biologically synthesized by several bacteria, notably, the strain of Acetobacter xylinum.¹ This fascinating and renewable polymer possesses remarkable chemical and physical attributes (e.g. high porosity, excellent mechanical strength, and large surface area, etc.) that can be applied in a wide range of bio-based materials and products.^2–4 Its wide applications have motivated researchers to focus on the fermentation process, especially to promote the BC yield. However, the fermentation process is extensively related to many aspects, such as the employed strains, medium conditions (carbon source, nutrients, pH, and dissolved oxygen), and incubation conditions (the employed medium volume, duration, surface area).^5–8Among these factors, the medium acidosis caused by the released organic acids, such as glucuronic acid and acetic acid, in the medium will negatively affect the BC biosynthesis during bacterial metabolism, which could weaken the bacteria activities and reduce the BC yield as a consequence. Generally, the pH of the BC fermentation medium can be dramatically decreased from 5.0 to lower than 2.0 during the incubation if no pH adjustment strategy was employed.^5,9,10 Current methods for BC incubation include static, agitated, and bioreactor cultures.¹¹ For agitated and bioreactor cultures, the regulation of pH is relatively easy because of the culture system is under stirring. However, the static culture of BC is still an ideal way to obtain high-quality BC membranes for many novel applications.^12–14 Unfortunately, it is quite difficult to adjust the pH of medium during the incubation because the formation of BC film in static culture will be seriously disturbed by the mechanical agitation. Therefore, to find an ingenious way to control the medium pH in a suitable range will be very critical to the BC production in practice.The essence of medium acidosis sources from the ionized hydrogen ions (H⁺) of the released organic acids in bacterial metabolic activity. If there is a proper approach to remove the H⁺ from culture medium in a controllable way, the BC production may significantly be promoted. Nowadays, the application of batteries has greatly facilitated people''s life. This revolutionary device was originated from the prototype of “galvanic cell” (or “voltaic piles”), which was invented by Alessandro Volta in 1800.¹⁵ Even now, the galvanic cell still be employed to demonstrate the mechanism of battery for the educational aim, such as the fruit battery.^16,17 Using lemons, oranges, grapefruits, potatoes, or apples which riches in citric acid, phosphoric acid, or malic acid as the electrolyte, and two different metallic electrodes were plugged into the fruit to form a battery. The fruit battery could provide continuous electricity to run various small devices, such as light-emitting diode (LED) and a digital clock. When the two metallic electrodes was connected with those devices by wire, the ionized H⁺ of organic acids inside of the fruit will be slowly consumed in anode and producing electric energy to drive those devices.^18–20 Inspired by the principle of a galvanic cell, we assumed that the ionized H⁺ of accumulated organic acids during the BC fermentation can be consumed in the anode of the built-in galvanic cell to form H₂, which will greatly weaken the acidified conditions of culture medium. Theoretically, a suitable pH condition for bacteria synthesis will promote the BC yield in a consequent. Meanwhile, the liberated metal ions from the cathode can serve as a suitable activator to the biochemical process of bacteria if the electrodes can be selected approximately, which also can potentially promote the BC yield.²¹ Based on this conception, the BC fermentation integrated a couple of electrodes to construct a galvanic cell system as its schematic diagram in Fig. 1 (the details of this built-in galvanic cell see ESI, page S2^†). To check the possibility of this first attempt, the BC yield of this newly constructed system (GC-medium) was compared with that of the normal medium, and the performance of electricity release was investigated as well.Open in a separate windowFig. 1Schematic diagram of the fermentation apparatus and the data acquisition system.The medium pH was monitored at every 12 h during static incubation as shown in Fig. 2.²² It could be easily found that the pH of the normal medium displayed a continuous decrease as the fermentation time was prolonged to 144 h. By contrast, the pH in the GC-medium firstly increased to 4.6 after 24 h of incubation, then maintained in the range from 4.2 to 4.4. Obviously, the medium pH for BC fermentation can be stabilized via loading the galvanic cell to consume the extra acids from the medium process.Open in a separate windowFig. 2Changes of medium pH during the incubation. Roman numerals of (I), (II), and (III) and Arabic numerals of (1) and (2) represent the stage of pH changes during the incubation in GC-medium and normal medium, respectively.Correspondingly, the BC yield from the GC-medium was 0.358 g L⁻¹, which was 2.9-fold higher than that of the normal medium (Fig. 3). Apparently, the pH adjustment by the galvanic cell can work well to yield more BC, verifying the possibility of the proposed conception. Besides, the residual glucose in the GC-medium was lower than that of the normal medium, as well as the residual glucuronic acid. These results again proved that more carbon source was converted into BC. When the BC film started to form at the air–liquid interface, the bacteria would be embedded into the film and fixed, which can result in a clearer medium. The relatively lower OD₆₁₀ in the GC-medium indicated that the more bacteria were fixed result from the thicker BC film that produced in GC-medium.²³ Moreover, the relatively higher DO (dissolved oxygen) was remained in the GC-medium after 6 days incubation also demonstrated that the conditions for cellulose biosynthesis of bacteria were better than that of the normal medium,²⁴ which also suggested more sugar will be consumed for BC synthesis once the galvanic cell was built during the fermentation process.Open in a separate windowFig. 3Medium conditions after 6 days incubation. BC referred to the yield of bacterial cellulose (g L⁻¹); OD₆₁₀ is the optical density of medium at 610 nm; DO is dissolved oxygen (mg L⁻¹); RG is residual glucose (g L⁻¹); GA is glucuronic acid (g L⁻¹). Analysis of variance (ANOVA): ***p < 0.001, * 0.01 < p < 0.05.The formed current with 2 Ω-load of the built-in galvanic cell can be detected by the digital multi-meter. As shown in Fig. 4a, the current decreased sharply from 2013 μA to 878 μA in the first 2 h, this result was related to the rapid consumption of the H⁺ that contained in the strain when the built-in galvanic cell was activated. When the bacteria started to self-replicate in the first 72 h, more organic acid was produced and released to the medium (refer to Fig. 2), which slowed down the rate of current reduction in the following 22 h. The prominent increase of current appeared in 24–72 h, proving that the medium was still rich in H⁺, meanwhile, the number of bacteria grew exponentially. These results also could be observed in Fig. 2, the changes of pH were well matched with the adjustment of the built-in galvanic cell. This correlativity between the medium pH and the formed current of GC has the potential to be designed as a fully automatic pH control system (ESI, Fig. S1^†).Open in a separate windowFig. 4Electricity generation performance during the incubation. (a) Current monitoring with 2 Ω resistor; (b) cumulative energy output in the whole BC fermentative production.Afterward, the current was maintained around 1163 μA during the following 3 days, which can demonstrate the amount of Acetobacter xylinum in GC-medium reach a stable period. Meanwhile, the pH of GC-medium was still within a suitable range of 4.2–4.4 while the pH of the normal medium has been reduced to around 2.7–2.8, which was already negative to the bacterial metabolic activities (Fig. 2). Generally, the death period of bacteria was mainly attributed to the medium acidosis.¹⁰ Hence, the mechanism of improving the BC yield by this built-in galvanic cell was to prevent the medium acidosis and maintained the activity of bacteria, which can stabilize the BC biosynthesis successfully.The cumulative energy output was calculated and showed in Fig. 4b, although the initial pH of GC-medium was relatively lower than that after 48 h, the energy output had a remarkable promotion. This result proved the major factors for the energy output was not only affected by the apparent medium pH but also related to the ability to provide H⁺ within bacteria metabolism. This ability was mainly contributed by the number of bacteria and the bacterial activity, which would be in a better condition if there was a built-in galvanic cell. Previous studies have suggested that the H⁺ concentration in the electrolyte, metal type of electrode, and the number of galvanic cells to be assembled in series are the key factors that influenced the output voltage of the galvanic cell.¹⁷ In this study, the magnesium (Mg) anode, copper (Cu) cathode, and the H⁺-rich culture medium formed an integrated galvanic cell system. The voltage was determined as 1.55–1.65 V for this built-in galvanic cell during the BC production, which can light the LED bulb (ESI, Fig. S2^†). Of course, it also can provide enough electricity to drive digital clocks, sensors, and other low-power devices in the whole incubation time. These results substantially proved that the conception of this work to produce electricity and promote BC production can be achieved via loading the built-in galvanic cell.The schematic mechanism diagram of acidification, pH adjustment, and electricity generation of the galvanic cell were illustrated with Fig. 5, the metabolic by-products, such as citric acid (CA), acetic acid (AC), gluconic acid (GLCA), and pyruvic acid (PA), are generally derived from the tricarboxylic acid (TCA) cycle, pentose phosphate pathway (HMP) and glycolytic pathway (EMP).²⁵ At the beginning of fermentation, glucose (GLC) in the medium was high enough to support the cell self-replication through the aerobic respiration of bacteria in the TCA cycle, which results in an amount of GLCA released to the medium. In this process, the by-products, such as CO₂, CA, and H₂O, also could be generated correspondingly. In addition, a considerable amount of AC and some PA can be released from the HMP and EMP, respectively.²⁴ These by-products, including GLCA, AC, CA, and PA or CO₂, were mainly responsible for medium acidosis, which inhibited bacteria activity and reduced the BC production as a consequence. Besides, the produced GLCA would inhibit the Acetobacter xylinum biosynthesis for BC.²⁶ The dissolved CO₂ in the medium also limited the aerobic respiration of bacteria, which will make the bacteria produce more CA and PA as a feedback regulation. This could create a vicious circle to deteriorate the medium pH and cease in BC production eventually. However, when the galvanic cell was built inside of the culture medium, those organic acids could provide the ionized H⁺ to maintain the galvanic reaction. The H⁺ would move to the Cu-electrode and be reduced as hydrogen gas by the acceptance of the electrons. The Mg-electrode would lose electrons and be oxidized to Mg²⁺, which can involve several cell life activities and potentially promote the BC yield (the effect of Mg²⁺ on BC production shown in ESI, Fig. S3^†). During this process, the directional transfer of electrons in the external circuit created the current, and the electric energy will be continuously output throughout the fermentation. It can image that this built-in galvanic cell can yield considerable power once a large-scale BC production was considered. Moreover, the conception of built-in galvanic cell in bioconversion processes that need pH control, such as anaerobic digestion of easy-acidification substrates, and ethanol fermentation by yeast can also be considered to apply this conception to maintain the stable and suitable pH.Open in a separate windowFig. 5The schematic mechanism diagram of acidification, pH adjustment, and electricity generation of the galvanic cell. GLC (glucose), GLCA (gluconic acid), CA (citric acid), AC (acetic acid), PA (pyruvic acid), GLC6P (glucose-6-phosphate), GLC1P (glucose-1-phosphate), UDPG (uridine diphosphoglucose), HMP (pentose phosphate pathway), FRU6P (fructose-6-phosphate), GAP (glyceraldehyde-3-phosphate), G3P (3-phosphoglycerate), PEP (phosphoenolpyruvate), PYR (pyruvate), ATP (adenosine triphosphate).     

超声心动图自动心肌运动定量技术对尿毒症透析患者早期左心室收缩功能的评估

目的探讨超声心动图自动心肌运动定量技术（aCMQ）评估不同透析时间段的尿毒症患者左心室收缩功能的价值。 方法选择2018年5月至2019年2月在浙江省杭州市萧山区第一人民医院血液透析室接受透析治疗的尿毒症患者52例。根据其接受血透时间的不同分为3组,A组为透析时间≤3年的患者,共27例;B组为透析时间＞3年且≤7年的患者,共16例;C组为透析时间＞7年的患者,共9例;正常对照组共60例,既往均无心脏及肾疾病病史,常规心电图及超声心动图检查均未见明显异常。首先运用M型超声心动图,通过Teichholz法获得病例组及对照组左心室射血分数（LVEF）,然后启动X-Plane技术采集4个心动周期的四腔心及两腔心,根据心电图指示分别描记左心室舒张末期及左心室收缩末期,运用双平面Simpson法分别计算出病例组及对照组LVEF,最后运用aCMQ分别获取病例组及对照组研究对象的左心室整体长轴应变（LVGLS）、心尖两腔心长轴应变（LVAP2LS）、心尖四腔心长轴应变（LVAP4LS）及心尖三腔心长轴应变（LVAP3LS）,分析不同透析年限组尿毒症患者左心室长轴应变变化。多组间比较采用方差分析,组间两两比较采用LSD-t检验。 结果Teichholz法测得病例组与对照组LVEF分别为：A组（67.21±6.63）%;B组（64.73±6.47）%;C组（64.58±8.38）%;对照组（67.02±3.62）%。Simpson法测得病例组与对照组LVEF分别为：A组（64.71±4.93）%;B组（64.08±6.02）%;C组（63.91±7.49）%;对照组（66.17±3.14）%。病例组与对照组LVEF比较以及病例组间LVEF比较,差异均无统计学意义（P均＞0.05）。运用aCMQ得到病例组与对照组LVGLS分别为：A组（-20.79±2.70）%、B组（-20.03±3.58）%、C组（-18.32±3.71）%、对照组（-24.39±2.05）%;LVAP4LS分别为：A组（-22.09±2.76）%、B组（-20.11±3.94）%、C组（-19.49±3.73）%、对照组（-24.61±2.37）%;LVAP3LS分别为：A组（-19.32±3.85）%、B组（-19.28±4.37）%、C组（-16.61±4.40）%、对照组（-23.53±6.18）%;LVAP2LS分别为：A组（-20.09±2.53）%、B组（-19.57±2.65）%、C组（-18.09±4.01）%、对照组（-23.51±7.52）%。病例组LVGLS、LVAP2LS、LVAP4LS及LVAP3LS的测值均较对照组减低,差异具有统计学意义（A组 vs 对照组：t=-5.949、-3.844、-6.117、-4.863,P均＜0.001;B组 vs 对照组：t=-5.883、-5.619、-5.036、-4.650,P均＜0.001;C组 vs 对照组：t=-6.541、-5.081、-6.130、-4.854,P均＜0.001）,其中A组LVGLS、LVAP4LS和LVAP3LS测值比C组减低,差异具有统计学意义（t=-2.493、-2.405、-2.012,P=0.014、=0.018、=0.047）,A组与C组LVAP2LS测值比较,差异无统计学意义（P＞0.05）,A组与B组间以及B组与C组间在LVGLS、LVAP2LS、LVAP3LS、LVAP4LS测值比较,差异也均无统计学意义（P均＞0.05）。 结论aCMQ能早期发现尿毒症透析患者左心室收缩功能的异常,为临床早期预防及治疗心功能衰竭提供了新的途径。     

自拟增液育胎方治疗妊娠晚期羊水过少的临床效果观察

目的:探讨自拟增液育胎方治疗妊娠晚期羊水过少的临床效果。方法:将2018年2月~2019年2月在某院产科治疗的120例妊娠晚期羊水过少患者随机分为观察组和对照组。对照组采用常规西医治疗,在此基础上观察组使用自拟增液育胎方治疗,比较两组患者的临床疗效、羊水和脐血流变化、分娩方式、妊娠结局。结果:观察组治疗有效率为83.33%,高于对照组的73.33%;观察组治疗后AFI、AFD明显高于对照组,而S/D明显低于对照组(P<0.05);观察组早产、新生儿窒息、新生儿低体重、新生儿Apgar评分≤7分等不良妊娠结局发生率明显低于对照组(P<0.05);观察组自然分娩率明显高于对照组,而剖宫产率明显低于对照组(P<0.05)。结论:自拟增液育胎方治疗妊娠晚期羊水过少的临床效果显著,能有效增加羊水量,改善胎盘血液循环,降低不良妊娠结局的发生率,提高自然分娩率,具有积极的临床意义。     

关于磷酸氯喹治疗新型冠状病毒肺炎给药方案的安全性刍议

国家卫生健康委员会和国家中医药管理局2020年2月18日发布的《新型冠状病毒肺炎诊疗方案(试行第六版)》将磷酸氯喹作为抗病毒试用药物之一,其后又于同月26日发布了《关于调整试用磷酸氯喹治疗新冠肺炎用法用量的通知》,2020年3月3日发布的《新型冠状病毒肺炎诊疗方案(试行第七版)》对磷酸氯喹给药方案进行了修订。磷酸氯喹半衰期长、全身分布广泛,易在体内蓄积,且不良反应与剂量相关。本文结合磷酸氯喹的药代动力学特点对给药方案进行了安全性分析,供临床医师和药师在诊治新型冠状病毒肺炎患者时参考,以降低发生不良反应的风险。     

酒石酸布托啡诺、地佐辛与盐酸托烷司琼在镇痛泵内配伍的稳定性考察

目的:考察酒石酸布托啡诺、地佐辛、盐酸托烷司琼在0.9%氯化钠注射液中的配伍稳定性。方法:模拟临床实际用药的配伍浓度和使用环境,检测0,1,4,6,24,48,72 h外观、pH、相对百分含量的变化。结果:酒石酸布托啡诺、地佐辛与盐酸托烷司琼的配伍液在72 h内pH未出现明显变化,外观稳定,各药品成分相对百分含量也没有明显变化。结论:在室温条件下,酒石酸布托啡诺、地佐辛与盐酸托烷司琼在0.9%氯化钠注射液中72 h内保持稳定。因此,酒石酸布托啡诺(6 mg)、地佐辛(20 mg)与盐酸托烷司琼(10 mg)可以配伍使用,在镇痛泵内配伍稳定。     

ICU患者影响万古霉素血药浓度的相关因素分析

目的 通过分析影响重症监护病房(ICU)患者万古霉素血药浓度的相关因素,探讨优化ICU患者万古霉素给药方案。方法 采用回顾性研究方法,收集东莞市人民医院ICU2016年1月至2018年9月使用并监测万古霉素血药浓度的出院患者。统计ICU患者万古霉素血药浓度分布情况,根据肌酐清除率(CrCl)将患者分为CrCl>90mL/min、CrCl 50~90mL/min、CrCl 10~50mL/min及CrCl<10mL/min 4组,分析不同肌酐清除率组对万古霉素血药浓度水平和达标率的影响以及比较指南推荐剂量与实际剂量的差别,并利用多重线性回归分析进一步探讨影响万古霉素血药浓度的相关因素。结果 99例ICU患者监测万古霉素血药浓度共230例次,45例次(19.57%)达到目标浓度(15~20mg/L),72例次(31.30%)未达标(<15mg/L),113例次(49.13%)超标(>20mg/L)。 CrCl 50~90mL/min和CrCl 10~50mL/min组平均血药浓度[(20.16±7.51)mg/L, (23.12±9.37)mg/L]、血药浓度超标比例(45.45%,62.79%)显著高于CrCl>90mL/min组[(14.65±9.07)mg/L, 19.15%]。CrCl>90mL/min、CrCl 50~90mL/min组实际剂量显著低于推荐剂量,而CrCl 10~50mL/min、CrCl<10mL/min组实际剂量显著高于推荐剂量。多重线性回归分析显示,给药剂量(B=11.631,95%CI=7.030~16.232,P<0.001)、肌酐清除率(B=-0.064,95%CI=-0.097~-0.032,P<0.001)、白蛋白水平(B=-0.334,95%CI= -0.634~-0.035,P=0.029)是影响ICU患者万古霉素血药浓度的主要相关因素。结论 ICU患者万古霉素血药浓度达标率较低,在优化ICU患者万古霉素给药方案时应考虑给药剂量、肌酐清除率和白蛋白水平因素的影响。     

Pharmacokinetics of different dosage of astragalus membranaceus of buyang huanwu decoction in rats with cerebral ischemic injury by microdialysis combined with LC/MS

To investigate the pharmacokinetics of effective components of Bu Yang Huang Wu Decoction (BYHWD) with different dosages of Astragalus (Yiqi groups and Huoxue groups ) applicating in rats with middle cerebral artery occlusion (MCAO). Replicating the animal model of cerebral ischemia-reperfusion in rats, establishing the liquid-mass spectrometry method for the determination of BYHWD and researching the pharmacokinetics of effective components of yiqi groups of BYHWD with different dosages of astragalus (3.09, 6.17, 12.34 g/Kg) and Huoxue goups (2.32 g/Kg) when applicated seperately in the rats suffering from cerebral ischemia reperfusion injury after femoral vein administration. The pharmacokinetics of formononetin and paeoniflorin in the different dosage groups of BYHWD met the one-compartment model, and the t_1/2 of formononetin and paeoniflorin in the low-dose Yiqi and Huoxue groups were (88.43±3.82, 69.18±0.11) min, MRT were (138.56±4.83, 113.62±2.42) min, and AUC_0–t were (28 488.35±4800.32, 140 614.80±23 954.05) ng/mL·min; The t_1/2 of formononetin and paeoniflorin in the middle-dose Yiqi group and Huoxue group were (82.16±1.78, 67.08±3.69) min, and MRT were (127.95±2.70, 116.58±4.13), AUC_0–t were (48 619.25±6745.75, 159 026.00±15 003.33) ng/mL·min; The t_1/2 of formononetin and paeoniflorin in the high-dose Yiqi and Huoxue groups were (80.29±1.12, 69.69±0.87) min, and MRT was (128.79±1.46, 118.78±4.56) min, AUC_0–t were (109 942.90±13 101.83, 189 417.90±22 311.00) ng/mL·min. The concentration rate of formononetin t_{1/2 brain} was decreased with increase of Astragalus dose. However, no significant difference between these two variables was found during experiments. Furthermore, the experiments showed that the increasing dose of astragalus would affect the pharmacokinetic behavior of paeoniflorin in the Huoxue groups. More specifically, the result showed that paeoniflorin can be metabolized more slowly in the body when applicated in high dose of the jaundice administration groups . In this way, the effect of paeoniflorin can be lasted for longer time in the body and brain.     

Cost-effectiveness analysis of second-line chemotherapy strategies for patients with advanced non-squamous non-small cell lung cancer

Lung cancer is the most widespread type of cancer and the primary cause of cancer-related death in the world. In this study, we aimed to analyze the cost-effectiveness of second-line chemotherapy strategies based on gemcitabine, pemetrexed, and docetaxel for advanced non-squamous non-small cell lung cancer patients in China.A Markov model based on three states, progression-free survival, progressed survival and death, was constructed to simulate the progression of the disease in a 6-year horizon. Sensitivity analysis was performed to evaluate the robustness of the model. The primary outcome of the model was the incremental cost-effectiveness ratio at a willingness-to-pay threshold of 3× per capita GDP of China in 2018 ($29 383). The baseline model results showed that the quality-adjusted life years over the course of the disease associated with second-line chemotherapy strategies were 0.233, 0.417 and 0.272 for gemcitabine, pemetrexed and docetaxel, respectively, and the corresponding total costs were $5321.02, $12 143.94, and $9479.42. Gemcitabine, pemetrexed and docetaxel resulted in the incremental cost-effectiveness ratios of $37 081.09 and $106 625.64 per quality-adjusted life year gained. The incremental cost-effectiveness ratio of pemetrexed and docetaxel compared with gemcitabine exceeded the willingness-to-pay threshold. One-way sensitivity analysis showed that the utility value of gemcitabine in the progressed survival state was the most influential parameter.