Kinetic modeling of cellulosic biomass to ethanol via simultaneous saccharification and fermentation: Part II. Experimental validation using waste paper sludge and anticipation of CFD analysis

Abstract

A kinetic model of cellulosic biomass conversion to ethanol via simultaneous saccharification and fermentation (SSF) developed previously was validated experimentally using paper sludge as the substrate. Adsorption parameters were evaluated based on the data obtained at various values for fractional cellulose conversion. The adsorption model was then combined with batch SSF data to evaluate the cellulose hydrolysis parameters. With the parameters evaluated for the specific substrate, the discrete model was able to predict SSF successfully both with discrete addition of cellulase only and with discrete feeding of substrate, cellulase, and media. The model tested in this study extends the capability of previous SSF models to semi-continuous feeding configurations, and invites a mechanistic interpretation of the recently observed trend of increasing conversion with decreasing feeding frequency [Fan et al. (2007a) Bioprocess Biosyst Eng 30(1):27-34]. Our results also support the feasibility and utility of determining adsorption parameters based on data obtained at several conversions, particularly when the model is to be applied to extended reaction times rather than only initial hydrolysis rates. The revised model is considerably more computationally efficient than earlier models, and appears for many conditions to be within the capability of simulation using computational fluid dynamics.

Ultrasound enhanced ethanol production from Parthenium hysterophorus: A mechanistic investigation

“…In this study, we have addressed this fundamental issue with approach of coupling experimental results of conventional (with mechanical agitation) as well as ultrasoundassisted fermentation to a mathematical model reported in literature (Gupta et al, 2012;Philippidis, 1992;Philippidis, 1993;Shao et al, 2009). This model comprises three simultaneous ordinary differential equations (ODE), one each for the time profiles of cell mass concentration, glucose concentration and ethanol concentration in the fermentation broth (Philippidis, 1992).…”

Reactor scale up for biological conversion of cellulosic biomass to ethanol

“…This suggests that reaction is the rate limiting step at N js , since reactor performance should increase due to increasing agitation if mass transfer were rate limiting as can be seen from Eqs. (14) to (17). Reaction is still the rate limiting step at the large scale analyzed in this study because the rate of mass transfer is still more than ten times higher than that of reaction based on conservative calculations.…”

“…Composition and SSF tests for the sludge have been reported in a previous study [17]. Spezyme CP cellulase was kindly provided by Genencor International, Inc. Novozyme 188 b-glucosidase was obtained from Sigma-Aldrich (St. Louis, MO).…”

“…The mixing requirements for subsequent reactors are less than that for the first reactor because of lower viscosity with increasing conversion. A typical conversion of 48% for the first reactor was chosen based on kinetic models described elsewhere [17,20] for the analysis with an initial cellulose concentration of 90 g/L. The reactor geometry for the analysis was based on an Applikon 3-L bioreactor with 1.6 L working volume.…”

Evaluation of the effect of a hydraulic impeller in a flocculation basin on hydrodynamic behavior using computational fluid dynamics

“…This code has been applied in various liquid or gas engineering problems [15,16]. The code uses the finite control volume method for the spatial discretization of the domain.…”