Bioethanol fuels from abundant biomass resources via fermentation have been long considered as an important bulk chemical and sustainable biofuel in the context of the circular economy. In the bioethanol production process, an indispensable step is the downstream separation of the dilute product from water-rich fermentation broth. This separation step was proved as one of the most energy-intensive steps in the whole bioethanol process and occupied a large percentage of the production cost. To decrease the energy requirement, continuous improvement of the bioethanol separation techniques was of great necessity. Compared with other emerging bioethanol separation technologies, distillation is a time-tested method and has been widely used in industry. This chapter is focused on the distillation for bioethanol separation. In the first part, the basic property of components in the bioethanol fermentation broth was introduced followed by discussing the thermodynamic behavior and the phase equilibrium. In the second part, the current advances and technical trends in bioethanol distillation, including the selection of sequences and process intensification, were reviewed. In the third part, techno-economic analysis and life cycle assessment models for bioethanol distillation are briefly introduced.
Abstract Increased absorption of visible light, low electron‐hole recombination, and fast electron transfer are the major objectives for highly effective photocatalysts in biocatalytic artificial photosynthetic systems. In this study, a polydopamine (PDA) layer containing electron mediator, [M], and NAD + cofactor was assembled on the outer surface of ZnIn 2 S 4 nanoflower, and the as‐prepared nanoparticle, ZnIn 2 S 4 /PDA@poly/[M]/NAD + , was used for photoenzymatic methanol production from CO 2 . Because of effective capturing of visible light, reduced distance of electron transfer, and elimination of electron‐holes recombination, a high NADH regeneration of 80.7±1.43 % could be obtained using the novel ZnIn 2 S 4 /PDA@poly/[M]/NAD + . In the artificial photosynthesis system, a maximum methanol production of 116.7±11.8 μ m was obtained. The enzymes and nanoparticles in the hybrid bio‐photocatalysis system could be easily recovered using the ultrafiltration membrane at the bottom of the photoreactor. This is due to the successful immobilization of the small blocks including the electron mediator and cofactor on the surface of the photocatalyst. The ZnIn 2 S 4 /PDA@poly/[M]/NAD + photocatalyst exhibited good stability and recyclability for methanol production. The novel concept presented in this study shows great promise for other sustainable chemical productions through artificial photoenzymatic catalysis.
The facile fabrication of low-cost photocatalysts with enhanced activity and high atomic utilization is becoming increasingly necessary for solar energy usage and/or conversion. In this work, a series of mesoporous carbon nitride nanosheets with an enlarged specific surface area was synthesized via an inorganic acid-assisted exfoliation method without any soft or hard templates. An ultralow loading of downsized noble metal Pt was anchored on these porous nanosheets, exhibiting enhanced photocatalytic activity. The formation of mesoporous nanosheets in carbon nitride was expected to boost the mass transfer and shorten the charge carrier transfer route during the photocatalytic reaction. The characterization of samples revealed that the enhanced conductivity and photocurrent of the carbon nitride nanosheets also contributed to the enhanced H2 evolution activity. The maximum H2 production rates of 172.92 μmol h-1 and 321 μmol h-1 were achieved over the nanosheets derived from melamine and urea under visible light irradiation, which are 10.92- and 2.22-fold that of the corresponding bulk carbon nitride, respectively. This exfoliation method was demonstrated to be an efficient and universal method for the preparation of carbon nitride nanosheets with a mesoporous structure and high atom utilization of the co-catalyst for H2 evolution from water.
Steam explosion (SE) is an effective and industrially scalable lignocellulose pretreatment method, which can be used for second-generation biobutanol production by acetone-butanol-ethanol (ABE) fermentation. Nevertheless, a series technical barrier such as the high inhibition of SE hydrolysate, low concentration, and low yield of ABE production hindered the availability of SE technique. In this study, aiming to solve the above obstacles and boosting cellulosic ABE production, the ABE fermentation process was intensified by a novel strategy that combine the pH adjusting with intermittent feeding. Results revealed that maintaining the pH at 6.5 for initial 12 h of cultivation ensures the smoothly shifting of the acidogenesis phase to solventogenesis phase of the C.acetobutylicum cells, so that eliminate the acid crash. While the lag period of fermentation was obvious shorted by intermittent feeding the concentrated SE hydrolysate into the diluted broth. Consequentially, 17.75 g/L of ABE (11.75 g/L of butanol) can be obtained within 48 h of fermentation, with the yield and productivity of 0.36 g/g (of sugars) and 0.37 g/L‧h, respectively. Correspondingly, 194.9 g of ABE (129.0 g of butanol) can be produced from 1 kg of dried corn stover .
The efficient recycling of waste electronic 3C products depends on the development of automatic disassembly process, including the robust vision detection system. Here we choose laptop parts as the target object, and build a dataset that contains 620 images. Our work focused on parts detection at disassembly scenario and implemented a universal and extensible laptop parts detector that can be applied to disassembly pipeline which based on a light and improved Mask R-CNN. After generating the mask images of parts, a rotary rectangle fitting method for parts was performed to predict the parts' rotation angle, and apply specific rules based on quantity and space constraints to improve the accuracy.
For decades micoorganisms have been engineered for the utilization of lignocellulose-based second-generation (2G) feedstocks, but with the concerns of increased levels of atmospheric CO2 causing global warming there is an emergent need to transition from the utilization of 2G feedstocks to third-generation (3G) feedstocks such as CO2 and its derivatives. Here, we established a yeast platform that is capable of simultaneously converting 2G and 3G feedstocks into bulk and value-added chemicals. We demonstrated that by adopting 3G substrates such as CO2 and formate, the conversion of 2G feedstocks could be substantially improved. Specifically, formate could provide reducing power and energy for xylose conversion into valuable chemicals. Simultaneously, it can form a concentrated CO2 pool inside the cell, providing thermodynamically and kinetically favoured amounts of precursors for CO2 fixation pathways, e.g. the Calvin–Benson–Bassham (CBB) cycle. Furthermore, we demonstrated that formate could directly be utilized as a carbon source by yeast to synthesize endogenous amino acids. The engineered strain achieved a one-carbon (C1) assimilation efficiency of 9.2%, which was the highest efficiency observed in the co-utilization of 2G and 3G feedstocks. We applied this strategy for productions of both bulk and value-added chemicals, including ethanol, free fatty acids (FFAs), and longifolene, resulting in yield enhancements of 18.4%, 49.0%, and ∼100%, respectively. The strategy demonstrated here for co-utilization of 2G and 3G feedstocks sheds lights on both basic and applied research for the up-coming establishment of 3G biorefineries.
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