The future of bioethanol

Yeasts have been domesticated by mankind before horses. After the mastering of alcoholic fermentation for centuries, yeasts have become the protagonist of one of the most important biotechnological industries worldwide: the production of bioethanol. This chapter will initially present some important challenges to be overcome in this industry, both in first and second generation biofuel production. Then, it will briefly revisit some advances obtained in recent years. Finally, it will present and discuss some opportunities, in the scope of metabolic engineering and synthetic biology, that will likely be present in the future of bioethanol

Electro-spinning/netting: A strategy for the fabrication of three-dimensional polymer nano-fiber/nets.

Since 2006, a rapid development has been achieved in a subject area, so called electro-spinning/netting (ESN), which comprises the conventional electrospinning process and a unique electro-netting process. Electro-netting overcomes the bottleneck problem of electrospinning technique and provides a versatile method for generating spider-web-like nano-nets with ultrafine fiber diameter less than 20 nm. Nano-nets, supported by the conventional electrospun nanofibers in the nano-fiber/nets (NFN) membranes, exhibit numerious attractive characteristics such as extremely small diameter, high porosity, and Steiner tree network geometry, which make NFN membranes optimal candidates for many significant applications. The progress made during the last few years in the field of ESN is highlighted in this review, with particular emphasis on results obtained in the author's research units. After a brief description of the development of the electrospinning and ESN techniques, several fundamental properties of NFN nanomaterials are addressed. Subsequently, the used polymers and the state-of-the-art strategies for the controllable fabrication of NFN membranes are highlighted in terms of the ESN process. Additionally, we highlight some potential applications associated with the remarkable features of NFN nanostructure. Our discussion is concluded with some personal perspectives on the future development in which this wonderful technique could be pursued

Literature review of physical and chemical pretreatment processes for lignocellulosic biomass

Different pretreatment technologies published in public literature are described in terms of the mechanisms involved, advantages and disadvantages, and economic assessment. Pretreatment technologies for lignocellulosic biomass include biological, mechanical, chemical methods and various combinations thereof. The choice of the optimum pretreatment process depends very much on the objective of the biomass pretreatment, its economic assessment and environmental impact. Only a small number of pretreatment methods has been reported as being potentially cost-effective thus far. These include steam explosion, liquid hot water, concentrated acid hydrolysis and dilute acid pretreatments

Attached-growth bioreactors for syngas fermentation to biofuel

Lignocellulosic biomass is a renewable resource for sustainable production of biofuels and chemicals. Syngas fermentation, a hybrid process integrating the thermochemical (i.e. gasification of feedstock to syngas) and biochemical (i.e. microbial fermentation of syngas) conversions, has been considered as a promising technology for production of lignocellulosic-biomass-derived ethanol. The challenge to commercialize syngas fermentation, though, is to enhance the gas-to-liquid mass transfer rate due to the low solubilities of carbon monoxide (CO) and hydrogen (H2) in an energy-efficient manner. Conventional suspended-growth bioreactors, such as continuous stirred tank reactor (CSTR) and bubble column reactor (BCR), suffer from inefficient mass transfer and unwanted cell washout at high dilution rate, resulting to low productivities. The present study explored the feasibility of applying three innovative attached-growth bioreactor systems, hollow fiber membrane biofilm reactor (HFM-BR), monolithic biofilm reactor (MBR) and rotating packed bed biofilm reactor (RPB-BR), in continuous syngas fermentation, in order to enhance mass transfer of CO and to maximize ethanol production, by optimizing selected operational parameters. The highest ethanol productivity of HFM-BR, MBR and RPB-BR was achieved at 3.44 g/L/day, 2.35 g/L and 6.70 g/L/day with optimized fermentation operational condition, respectively. HFM-BR showed the highest CO kLa (1096.2 hour-1) among the three bioreactor systems; however, the costly membrane and biofouling issue are the drawbacks to conduct continuous syngas fermentation with high ethanol productivity for extended period of time. MBR showed modest performance of CO mass transfer rate and ethanol productivity, but it has inherent advantages such as high mechanical strength and less biofouling problem. With installation of an in-situ washing device, the microchannel-clogging problem could potentially be resolved, indicating its capability of extended periods of continuous fermentation. RPB-BR gave the highest ethanol productivity with a simple mechanical design, inexpensive packing media and stable operation. The present study demonstrated the great potential of attached-growth bioreactors as efficient systems to obtain syngas fermentation with high productivity of ethanol, making cellulosic ethanol biorefinery move one step forward to technical and economic feasibility. Ultimately, it is believed that this study will contribute to our nation\u27s independence from petroleum fuels