William R. Gibbons

Historical perspective of biofuels: learning from the past to rediscover the future

This issue of in vitro plant is dedicated to various aspects of biofuel research and development. The editors have sought the experts in this field and solicited manuscripts for this special issue publication from various academic institutions, government (USDA, DOE), industry (Mendel, Alellyx, Canavilas, Syngenta, Monsanto), and various countries (USA, China, Brazil, India, and Australia). This has resulted in state-of-the-art articles describing ethanol and also biodiesel research. These publications highlight the status of biofuel research across the globe and also focus on private, public, and government interests. This is especially noteworthy in that President Barack Obama has stated that renewable energy is a pivotal aspect of his policy for the USA. The objective of this introduction is to provide the reader with the pertinent background information relative to the biofuel efforts within the private sector, academia, and government laboratories. In particular, the history of biofuel research and commercialization is provided as well as a summary of the various crop systems available for biofuel production.

Integrated Biorefineries with Engineered Microbes and High-value Co-products for Profitable Biofuels Production

Corn-based fuel ethanol production processes provide several advantages which could be synergistically applied to overcome limitations of biofuel processes based on lignocellulose. These include resources such as equipment, manpower, nutrients, water, and heat. The fact that several demonstration-scale biomass ethanol processes are using corn as a platform supports this viewpoint. This report summarizes the advantages of first-generation corn-based biofuel processes and then describes the technologies, advantages, and limitations of second-generation lignocellulose-based biofuel systems. This is followed by a discussion of the potential benefit of fully integrating first- and second-generation processes. We conclude with an overview of the technology improvements that are needed to enhance the profitability of biofuel production through development of an integrated biorefinery. A key requirement is creation of industrially robust, multifunctional ethanologens that are engineered for maximum ethanol production from mixed sugars. In addition to ethanol, combined biorefineries could also be the source of valuable co-products, such as chemicals and plastics. However, this will require expression systems that produce high-value co-products. Advantages of this approach are that (1) such strains could be used for bioconversion in any part of the combined biorefinery and (2) using one recombinant organism with many additions should simplify the process of obtaining necessary FDA approval for feed products produced by or containing recombinant organisms.

Conversion of volatile fatty acids into polyhydroxyalkanoate by Ralstonia eutropha

Aims:  The aims of this study were to optimize condensed corn solubles (CCS) as a medium for growth of Ralstonia eutropha and to determine the effects of individual volatile fatty acids (VFAs) on polyhydroxyalkanoate (PHA) production.

Enzyme recycling in a simultaneous and separate saccharification and fermentation of corn stover: A comparison between the effect of polymeric micelles of surfactants and polypeptides

The efficacy of enzyme recycling in simultaneous (SSF) and separate (SHF) saccharification and fermentation of corn stover was evaluated with the use of novel enzyme stabilizers of casein, Tween20 and polymeric micelles (PMs) of polyethylene glycol (PEG)-casein and PEG-Tween20. Amphiphiles were added to maximize the percentage of enzyme remaining in fermented liquor that could be recycled twice back into the process. With no additive, in SHF the ethanol yield was declined by 64.0% and 80.0% after the first and second recycling, respectively. Application of PMs of PEG-casein in one cycle of SHF significantly improved the theoretical ethanol yield from 0.49 ± 0.00 to 0.91 ± 0.00 g/g compared to when only casein (0.66 ± 0.00 g/g), Tween 20 (0.53 ± 0.00 g/g) and Tween 20-PEG (0.77 ± 0.08 g/g) were used. PMs of PEG-Tween and PEG-casein also improved enzyme recycling, such that the ethanol yield was improved by 50% and 108% beyond that obtained with Tween and casein, respectively.

Neutralization/recovery of lactic acid from Lactococcus lactis: effects on biomass, lactic acid, and nisin production.

Besides lactic acid, many lactic acid bacteria also produce proteinaceous metabolites (bacteriocins) such as nisin. As catabolite repression and end-product inhibition limit production of both products, we have investigated the use of alternative methods of supplying substrate and neutralizing or extracting lactic acid to increase yields. Fed-batch fermentation trials using a stillage-based medium with pH control by NH4OH resulted in improved lactic acid (83.4 g/l, 3.18 g/l/h, 95% yield) and nisin (1,260 IU/ml, 84,000 IU/l/h, 14,900 IU/g) production. Removing particulate matter from the stillage-based medium increased nisin production (1,590 IU/ml, 33,700 IU/g), but decreased lactic acid production (58.5 g/l, 1.40 g/l/h, 96% yield). Removing lactic acid by ion exchange resins stimulated higher lactic acid concentrations (60 to 65 g/l) and productivities (2.0 to 2.6 g/l/h) in the filtered stillage medium at the expense of nisin production (1,500 IU/ml, 25,800 IU/g).

Cofermentation of sweet sorghum juice and grain for production of fuel ethanol and distillers' wet grain

Abstract In an attempt to reduce the costs associated with fuel ethanol production from grain, the authors used sweet sorghum juice as a partial or complete replacement for tap-water in mash preparation and fermentation. This juice, which was an unutilized by-product of sweet sorghum silage preservation by the Ag-Bag method, contained 6·5–7·6% (wt/wt) reducing sugar and produced up to 3·51% (v/v) ethanol beers after fermentation. Varying amounts of this juice were mixed with water and corn or wheat, either before or after liquefaction (front-end or back-end loading, respectively). When over 60% juice replacement was used in front-end loading trials, salt buildup, due to required pH adjustments during cooking, inhibited yeast metabolism and thereby reduced yields. This inhibition was not observed during back-end loading trials since acid and base usage during cooking were reduced. However, in all trials we noted yeast inhibition by some factor(s) present in juice from sweet sorghum variety NK 8368. This inhibition was not observed with variety NK 405. If sweet sorghum juice is used to replace 40% of the water and either 12·5% of the corn or 12% of the wheat in mash preparation, production costs can be reduced by

Use of potassium meta bisulfite to control bacterial contaminants during fermentation of fodder beet cubes for fuel ethanol

0.032/liter (

Effect of Extruder Screw Speed, Temperature, and Enzyme Levels on Sugar Recovery from Different Biomasses

0.12/US gallon) for corn and

Rhodospirillum rubrum: utilization of condensed corn solubles for poly‐(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) production

0.040/liter (

Solid phase fermentation of foder beets for ethanol production: Effect of grind size

0.15/US gallon) for wheat.