Production of 2,3-Butanediol from Sucrose by a <Emphasis Type="Italic">Klebsiella</Emphasis> Species

Chemical 2,3-butanediol is an important platform compound possessing diverse industrial applications. So far, it is mainly produced by using petrochemical feedstock which is associated with high cost and adverse environmental impacts. Hence, finding alternative routes (e.g., via fermentation using renewable carbon sources) to produce 2,3-butanediol are urgently needed. In this study, we report a wild-type Klebsiella sp. strain XRM21, which is capable of producing 2,3-butanediol from a wide variety of carbon sources including glucose, sucrose, xylose, and glycerol. Among them, fermentation of sucrose leads to the highest production of 2,3-butanediol. To maximize the production of 2,3-butanediol, fermentation conditions were first optimized for strain XMR21 by using response surface methodology (RSM) in batch reactors. Subsequently, a fed-batch fermentation strategy was designed based on the optimized parameters, where 91.2 g/L of 2,3-butanediol could be produced from substrate sucrose dosing in 100 g/L for three times. Moreover, random mutagenesis of stain XMR21 resulted in a highly productive mutant strain, capable of producing 119.4 and 22.5 g/L of 2,3-butanediol and ethanol under optimized fed-batch fermentation process within 65 h with a total productivity of 2.18 g/L/h, which is comparable to the reported highest 2,3-butanediol concentration produced by previous strains. This study provides a potential strategy to produce industrially important 2,3-butanediol from low-cost sucrose.     

Identification of peptide inhibitors of penicillinase using a phage display library

There is a constant need to identify novel inhibitors to combat β-lactamase-mediated antibiotic resistance. In this study, we identify three penicillinase-binding peptides, P1 (DHIHRSYRGEFD), P2 (NIYTTPWGSNWS), and P3 (SHSLPASADLRR), using a phage display library. Surface plasmon resonance (SPR) is utilized for quantitative determination and comparison of the binding specificity of selected peptides to penicillinase. An SPR biosensor functionalized with P3-GGGC (SHSLPASADLRRGGGC) is developed for detection of penicillinase with excellent sensitivity (15.8 RU nM⁻¹) and binding affinity (K_D = 0.56 nM). To determine if peptides can be good inhibitors for penicillinase, these peptides are mixed with penicillinase and their inhibition efficiency is determined by measuring the hydrolysis of substrate penicillin G using UV–vis spectrophotometry. Peptide P2 (NIYTTPWGSNWS) is found to be a promising penicillinase inhibitor with a K_i of 9.22 μM and a K_i′ of 33.12 μM, suggesting that the inhibition mechanism is a mixed pattern. This peptide inhibitor (P2) can be used as a lead compound to identify more potent small molecule inhibitors for penicillinase. This study offers a potential approach to both detection of β-lactamases and development of novel inhibitors of β-lactamases.     

Heme oxygenase 1 regulates apoptosis induced by heat stress in bovine ovarian granulosa cells via the ERK1/2 pathway

Heat stress can inhibit follicular development in dairy cows, and thus can affect their reproductive performance. Follicular granulosa cells can synthesize estrogen, that affects the development and differentiation of follicles by apoptosis. Heme oxygenase 1 (HO-1/heat shock protein 32) plays an antiapoptotic and cytoprotective role in various cells during stress-induced apoptosis, but little is known about its definitive function in bovine (ovarian) granulosa cells (bGCs). In our study, the roles and mechanism of HO-1 on the heat stress-induced apoptosis of bGCs were studied. Our results show that the expression of HO-1 was significantly increased under heat stress. Moreover, HO-1 silencing increased apoptosis, whereas its overexpression dampened apoptosis by regulating the expression of Bax/Bcl-2 and the levels of cleaved caspase-3. In addition, HO-1 can also play a cytoprotective role by affecting estrogen levels and decomposing heme to produce biologically active metabolite carbon monoxide (CO). Meanwhile, CO significantly increased the level of HO-1, decreased Bax/Bcl-2 levels, and inhibited the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway. The apoptosis of ovarian GCs can affect the secretion of estrogen and lead to disorder of the ovarian microenvironment, thus affecting the normal function of the ovary. Our results indicate that HO-1 acts as a cytoprotective enzyme and plays a protective role in heat-induced apoptosis of bGCs. In conclusion, HO-1 and its metabolite CO inhibit the apoptosis of bGCs induced by heat stress through the ERK1/2 pathway. The results of this study provide a valuable clue for improving the fertility of heat stressed cows in summer.     

Chemerin induces lipolysis through ERK1/2 pathway in intramuscular mature adipocytes of dairy bull calves

The adipokine Chemerin has been reported to regulate differentiation and metabolism of adipocytes, but the mechanism underlying lipolysis is still largely unknown. The purpose of this study was to explore whether ERK1/2 pathway is involved in regulating Chemerin during bovine intramuscular mature adipocyte lipolysis. Intramuscular mature adipocytes of dairy bull calves were cultured in vitro and were treated with Chemerin or U0126, which is an inhibitor of ERK1/2 pathway. The results showed that TG content in cells was significantly decreased, glycerol and free fatty acid were significantly increased in cell culture media, and the expression of phosphorylated ERK1/2 in cells was increased in Chemerin-treated group, suggested that ERK1/2 pathway was involved in regulation of lipolysis by Chemerin. In addition, the expression of lipolytic-related critical factors ATGL, HSL, LPL, PPARα, UCP3, and CPT1 were upregulated, but the expression of adipogenic key factors, including PPARγ and C/EBPα were downregulated by Chemerin. Interestingly, all the effects of Chemerin on genes expression in intramuscular mature adipocytes or fat tissue were inhibited by U0126, showed that the function of Chemerin to promote adipose decomposition will be significantly weakened if the ERK1/2 pathway is suppressed, and confirmed that ERK1/2 pathway is involved in mediate Chemerin-enhanced lipolysis. In conclusion, the study demonstrated that Chemerin induce intramuscular mature adipocytes lipolysis through activation of the ERK1/2 pathway. Our research at least provide partial mechanisms of Chemerin on lipolysis and deposition of intramuscular fat tissue of dairy bull calves.     

飘香藤的组织培养与快速繁殖

1植物名称飘香藤(Dipladenia sanderi Hemsl.)。2材料类别顶芽。3培养条件不定芽启动、丛生芽增殖培养基:(1)MS 6-BA 6.0 mg·L~(-1)(单位下同) NAA 0.2;(2) MS 6-BA 2.0 NAA 0.2;(3)MS 6-BA 0.5 NAA     

虎颜花的无菌播种和试管育苗

1植物名称虎颜花(TigridiopalmamagnificaC.Chen)。2材料类别种子。3培养条件种子萌发培养基:(1)MS;(2)1/2MS(大量元素用量减半);(3)1/4MS(大量元素用量为1/4);(4)1/8MS(大量元素用量为1/8);(5)1/4MS+NAA0.5mg·L-1(单位下同);(6)1/4MS+100mL·L-1椰子乳。丛生芽增殖培养基:(7)MS+6-BA10.0+NAA1.0;(8)MS+6-BA5.0+NAA0.5。壮苗培养基:(9)MS+6-BA2.0+NAA0.2;(10)MS+6-BA1.0+NAA0.1。生根培养基:(11)MS+NAA0.5;(12)MS+NAA0.5+0.1%活性炭;(13)MS+NAA0.5+0.2%活性炭。以上培养基均附加MS培养基的维生素和肌醇成分、20…     

Development of electrochemical calcium sensors by using silicon nanowires modified with phosphotyrosine

This paper reports the electrical detection of calcium ions by using silicon nanowires (SiNWs) as channels in a chemically gated field-effect-transistor (FET) configuration. To obtain a selective and sensitive layer for calcium sensing, the SiNWs are modified with a biologically relevant amino acid phosphotyrosine (p-Tyr), which is able to complex calcium ions with high affinity. It is found that when the p-Tyr modified SiNWs are exposed to aqueous solutions containing calcium ions, their conductances increase with the increasing of calcium concentration up to 10microM. In contrast, when the SiNWs are exposed to sodium or potassium, or when they are modified with tyrosine (Tyr), no significant increase in the conductance is observed. This finding suggests that the calcium ions complexed with the phosphate group of p-Tyr can act as a positive gate voltage on the FET device comprising of n-type SiNWs, and leads to an increase in their conductances. The FET device is also sensitive to magnesium ions. However, the response is 10 times lower than that of calcium at the same concentration. The study reported here may pave the way for designing an intracellular calcium sensor which permits the monitoring of calcium concentration in real time.     

豹斑火焰兰的离体快速繁殖

1 植物名称豹斑火焰兰(Renanthera monachica Ames). 2 材料类别种子. 3 培养条件种子萌发培养基:(1)VW;(2)VW+100 mL·L-1椰子乳;(3)1/2MS;(4)1/2MS+椰子乳100 mL·L-1.