Sue E. Nokes

The use of high-solids loadings in biomass pretreatment - a review.

The use of high‐solids loadings (≥15% solids, w/w) in the unit operations of lignocellulose conversion processes potentially offers many advantages over lower‐solids loadings, including increased sugar and ethanol concentrations and decreased production and capital costs. Since the term lignocellulosic materials refers to a wide range of feedstocks (agricultural and forestry residues, distillery by‐products, and dedicated energy crops like grasses), the term “solids loading” here is defined by the amount of dry material that enters the process divided by the total mass of material and water added to the material. The goal of this study is to provide a consolidated review of studies using a high‐solids pretreatment step in the conversion process. Included in this review is a brief discussion of the limitations, such as the lack of available water to promote mass transfer, increased substrate viscosity, and increased concentration of inhibitors produced affecting pretreatment, as well as descriptions and findings of pretreatment studies performed at high solids, the latest reactor designs developed for pretreatment at bench‐ and pilot‐scales to address some of the limitations, and high‐solids pretreatment operations that have been scaled‐up and incorporated into demonstration facilities. Biotechnol. Bioeng. 2012; 109:1430–1442.

Development of a Biologically Based Aerobic Composting Simulation Model

A relatively simple dynamic model based on microbial process kinetics has been developed for aerobic composting. Differential equations describing microbial, substrate, and oxygen concentrations, as well as moisture and temperature profiles have been derived as a function of vessel size and aeration rate. Microbial biomass growth was described using Monod growth kinetics as a function of degradable substrate concentration, oxygen concentration, moisture content, and compost temperature. Facility and fan operating costs have been included to permit economic optimization of the process. Predicted results demonstrated the ability of the model to quantify and describe the influence of multiple interacting factors (temperature, oxygen, moisture, and substrate availability) on the process driving the composting: microbial growth kinetics. Future development of the approach should be undertaken to provide a robust engineering model that can be used to evaluate and design environmentally sound composting facilities. An example application is presented along with data from a laboratory scale composter.

Production of phytase by Aspergillus niger in submerged and solid-state fermentation

Abstract Qualitative relationships between medium composition, Aspergillus niger morphology, and phytase production were investigated in submerged (SmF) and solid-state fermentations (SSF). Media composition and fungal morphology greatly affected phytase production in submerged culture. Addition of wheat bran, and consequently addition of a slow releasing organic phosphate source, enhanced A. niger growth and phytase production, in submerged and solid state culture. The fungal morphology in the presence of wheat bran changed from pelleted to filamentous in submerged culture. Filamentous mycelium and small pellets resulted in higher phytase activities than large pellets. Inoculation of solid-state fermentations with small pellets and free mycelial trees resulted in all cases in increased phytase activities. Large pellets were not suitable as a morphological form for SSF inoculum, unless they were homogenized. Homogenized large pellets led to SSF productivities similar to those from filamentous mycelia, irrespective of the medium type on which they were grown.

Economic Analysis of Cellulase Production Methods for Bio-Ethanol

The cost of cellulase enzymes has limited the feasibility of producing ethanol from fibrous biomass. Traditional submerged fermentation (SmF) was compared to an alternative method of producing cellulase, solid state cultivation (SSC). Results from an economic analysis indicated that the unit costs for cellulase enzyme production were

Compressed solvents for the extraction of fermentation products within a hollow fiber membrane contactor

15.67 (The prices are all 2004 prices in this article, except otherwise stated. We deflated newer prices to 2004 prices using a deflation factor 0.9 per year and inflated older prices to 2004 prices using an inflation factor 1.1.) per kilogram (

MANIPULATION OF HIGH SPATIAL RESOLUTION AIRCRAFT REMOTE SENSING DATA FOR USE IN SITE-SPECIFIC FARMING

/kg) and

Analysis of composition and structure of Clostridium thermocellum membranes from wild-type and ethanol-adapted strains

40.36/kg, for the SSC and SmF methods, respectively, while the corresponding market price was over

Screening of thermophilic anaerobic bacteria for solid substrate cultivation on lignocellulosic substrates.

90.00/kg. A sensitivity analysis conducted using Monte Carlo simulation also suggests that the unit cost of production using the SSC method is lower than the unit cost of production using SmF with a certainty of 99.6% (9,959 out of 10,000 cases). These results indicate that the SSC method may be a more economical method of cellulase production, thereby reducing bio-ethanol production costs. SSC may increase the potential that bio-ethanol will become a viable supplemental fuel source in light of current economic, political, and environmental issues.

Investigation of the metabolic inhibition observed in solid-substrate cultivation of Clostridium thermocellum on cellulose

Abstract The feasibility of extracting aqueous ethanol and acetone within a hollow fiber membrane contactor (HFC) has been examined using compressed CO 2 (69 bar), ethane (69 bar), and propane (34.5 bar) at ambient temperature. Ethanol and acetone were chosen as ‘model’ fermentation products to further examine the potential for extractive fermentation with compressed fluids. Aqueous and compressed solvent streams were contacted within a single hydrophobic isotactic polypropylene membrane fiber (0.6 mm ID; 106.7 cm in length; 75% porosity), providing a porous barrier between the two immiscible phases. The amount of solute extracted was determined as a function of the aqueous flowrate (tubeside) and molar solvent to feed ratio. The amount of aqueous ethanol (10 wt.%) and acetone (10 wt.%) extracted from binary feed solutions with compressed propane ranged from 6.4 to 14.3% and 21.8 to 90.6%, respectively, as a function of the aqueous flowrate (0.1 to 2 ml/min) and molar solvent to feed ratio ( S/F =1 to 10). Comparatively, ethanol extraction with compressed CO 2 ranged from 4.7 to 31.9% with similar variations in the aqueous flowrate (0.1 to 1 ml/min) and molar solvent to feed ratio (3 and 10). Acetone extracted with CO 2 ranged from 67.9 to 96.1% when varying the aqueous flowrate (0.1 to 1 ml/min) at a molar solvent to feed ratio of 3. Ternary ethanol/acetone/water mixtures were also examined to determine the effect of multi-solute aqueous solutions. The effect of aqueous and compressed fluid flows on extraction are interpreted based on the equilibrium distributions of the solutes between water and the compressed fluid (estimated using a group contribution association equation of state (GCA–EOS)) and the mass transfer characteristics of the compressed fluid.

OPTIMIZATION OF SOLID-STATE FERMENTATION PARAMETERS FOR THE PRODUCTION OF XYLANASE BY TRICHODERMA LONGIBRACHIATUM ON WHEAT BRAN IN A FORCED AERATION SYSTEM

Three spatial data sets consisting of high spatial resolution (1 m) remote sensing images acquired in 12 spectral bands, an on-the-go yield map, and a Digital Elevation Model were co-registered and evaluated for spatial variability studies in a Geographic Information Systems environment. Separate on-the-go yield maps were developed for 3, 5, and 12 statistically significant mean yield classes. For each yield class, the corresponding mean spectral and elevation data were extracted. The relationship between mean spectral and yield data was strongly linear (r = 0.99). Also, a strong linear relationship between mean yield and elevation data (r = 0.92) was found. The relationship between the spectral and on-the-go yield data indicated the potential of remote sensing for spatial variability studies. Keywords. Remote sensing, GIS, On-the-go yield, DEM, Precision farming.