·聚焦生物能源·

細(xì)菌或許是解決可持續(xù)能源問題的關(guān)鍵

研究人員對(duì)大腸桿菌的脂肪酸路徑進(jìn)行操縱，并用該生物自身反應(yīng)機(jī)制以一種可再生的方式生成丙烷。雖然最初產(chǎn)率低，但能夠通過識(shí)別和添加必要的生物化學(xué)成分以助推該生物合成反應(yīng)，從而使得特定的大腸桿菌菌種能夠合成相當(dāng)大數(shù)量的丙烷。重要的是，這一丙烷生成路徑能在有氧存在的情況下操作，這為該系統(tǒng)應(yīng)用于藍(lán)細(xì)菌(以太陽光能為主要能量來源、低營養(yǎng)需求的細(xì)菌)開辟了道路。

論文鏈接:Kallio P，Pásztor A，Thiel K，et al..An engineered pathway for the biosynthesis of renewable propane.

The deployment of next-generation renewable biofuels can be enhanced by improving their compatibility with the current infrastructure for transportation，storage and utilization.Propane，the bulk component of liquid petroleum gas，is an appealing target as it already has a global market.In addition，it is a gas under standard conditions，but can easily be liquefied.This allows the fuel to immediately separate from the biocatalytic process after synthesis，yet does not preclude energy-dense storage as a liquid.Here we report，for the first time，a synthetic metabolic pathway for producing renewable propane.The pathway is based on a thioesterase specific for butyryl-acyl carrier protein(ACP)，which allows native fatty acid biosynthesis of the Escherichia coli host to be redirected towards a synthetic alkane pathway.Propane biosynthesis is markedly stimulated by the introduction of an electron-donating module，optimizing the balance of O2supply and removal of native aldehyde reductases.

提高植物細(xì)胞油脂含量的新途徑

小球藻可作為生產(chǎn)生物柴油的原料，但含油量相對(duì)較低，研究人員將大豆的轉(zhuǎn)錄因子GmDof4基因轉(zhuǎn)入橢圓小球藻，在異養(yǎng)條件下GmDof4過表達(dá)的藻株含油量比對(duì)照提高46.4% ～52.9%，而藻株的生長率并沒有受到影響。轉(zhuǎn)錄組分析表明，轉(zhuǎn)基因藻株含油量的提高歸因于大量相關(guān)基因的表達(dá)被GmDof4所調(diào)控，特別是乙酰輔酶A羧化酶的表達(dá)和酶活性被顯著上調(diào)。

論文鏈接:Zhang J H，Hao Q，Bai L，et al..Overexpression of the soybean transcription factor GmDof4 significantly enhances the lipid content of Chlorella ellipsoidea.

Biotechnology for Biofuels，2014，7:128.doi:10.1186/s13068 －014 －0128 －4.

Abstract:The lipid content of microalgae is regarded as an important indicator for biodiesel.Many attempts have been made to increase the lipid content of microalgae through biochemical and genetic engineering.Significant lipid accumulation in microalgae has been achieved using biochemical engineering，such as nitrogen starvation，but the cell growth was severely limited.However，enrichment of lipid content in microalgae by genetic engineering is anticipated.In this study，GmDof4 from soybean(Glycine max)，a transcription factor affecting the lipid content in Arabidopsis，was transferred into Chlorella ellipsoidea.We then investigated the molecular mechanism underlying the enhancement of the lipid content of transformed C.ellipsoidea.We constructed a plant expression vector，pGmDof4，and transformed GmDof4 into C.ellipsoidea by electroporation.The resulting expression of GmDof4 significantly enhanced the lipid content by 46.4 to 52.9% ，but did not affect the growth rate of the host cells under mixotrophic culture conditions.The increase in lipid content could be attributed to the large number of genes with regulated expression.In particular，the acetyl-coenzyme A carboxylase gene expression and enzyme activity were significantly upregulated in the transgenic cells.Our research provides a new way to increase the lipid content of microalgae by introducing a specific transcription factor to microalgae strains that can be used for the biofuel and food industries.

基于細(xì)菌表面展示酶的生物燃料電池

研究人員利用生物模板法在氟摻雜二氧化錫(FTO)導(dǎo)電玻璃上制備出具有三維多孔結(jié)構(gòu)的金膜，并以此作為電極共價(jià)固定漆酶，制成生物陰極。該三維多孔金膜可顯著地提高酶的固定效率，并實(shí)現(xiàn)直接電子傳遞。生物陽極則采用細(xì)菌表面展示的葡萄糖脫氫酶突變體(bacteria-GDH)。電池在連續(xù)工作55 h后仍可保持84%的最大功率密度，表現(xiàn)出較高的穩(wěn)定性。

論文鏈接: Chuantao H，Dapeng Y，Bo L，et al..Enhanced performance of a glucose/O2biofuel cell assembled with laccase-covalently immobilized three-dimensional macroporous gold film-based biocathode and bacterial surface displayed glucose dehydrogenase-based bioanode.

Bioanode.Anal.Chem.，2014，86(12):6057 －6063.doi:10.1021/ac501203n.

Abstract:The power output and stability of enzyme-based biofuel cells(BFCs)is greatly dependent on the properties of both the biocathode and bioanode，which may be adapted for portable power production.In this paper，a novel highly uniform three-dimensional(3D)macroporous gold(MP-Au)film was prepared by heating the gold"supraspheres"，which were synthesized by a bottom-up protein templating approach，and followed by modification of laccase on the MP-Au film by covalent immobilization.The as-prepared laccase/MP-Au biocathode exihibited an onset potential of 0.62 V versus saturated calomel electrode(SCE，or 0.86 V vs NHE，normal hydrogen electrode)toward O2reduction and a high catalytic current of 0.61 mAcm－2.On the other hand，mutated glucose dehydrogenase(GDH)surface displayed bacteria(GDH-bacteria)were used to improve the stability of the glucose oxidation at the bioanode.The as-assembled membraneless glucose/O2fuel cell showed a high power output of 55.8 ± 2.0 μW cm－2and open circuit potential of 0.80 V，contributing to the improved electrocatalysis toward O2reduction at the laccase/MP-Au biocathode.Moreover，the BFC retained 84%of its maximal power density even after continuous operation for 55 h because of the high stability of the bacterial surface displayed GDH mutant toward glucose oxidation.Our findings may be promising for the development of more efficient glucose BFC for portable bat tery or self-powered device applications.