anaerobic digestion in the biorefinery market economy

S74 Special Abstracts / Journal of Biotechnology 150S (2010) S1–S576

[I.14]

Anaerobic digestion in the biorefinery market economy

W. Verstraete ∗

Ghent University, BelgiumKeywords: Anaerobic digestion; Biorefinery

Anaerobic digestion currently has gained powerful public atten-tion and political importance. Indeed, the bio-economy has startedand whatever processes in the so-called biorefineries are used, onehas to deal with a coherent set of downstream processes. In suchdownstream processing, the biomethanation technology is the keyto overall sustainable design and operation. As a result, the numberof digesters and particularly the overall digester capacity is risingsubstantially worldwide.

First an overview is given of the recent developments in thefield of biomethanation. Important progress has been made inpathway mapping and flux balance modelling of the digestionprocesses. Secondly, insights in the microbial ecology by the devel-opment of molecular microbiology based parameters such as therange-weighted species richness, the dynamics of change in thecommunity and also the environmental Pareto index, generatenew possibilities to provide better management of the poly-speciesbased biocatalyst responsible for the methane production.

Subsequently, the technical integration of anaerobic digestionin the biorefinery market economy is addressed. Aspects such asthe combination of biomethanation and bioelectrochemical sys-tems, the enhanced recovery of phosphate, nitrogen, calcium orsulfur and even NEWater in relation to digestion have become ofeconomic importance.

Furthermore, the possibilities of digesting energy crops andalgal poly-cultures respectively bagasse biomass in particular areof interest. Finally, the direct route going from biomass over biogasto commodity chemistry is also coming into focus due to progressin the conversion of methane to methanol.

Overall, anaerobic digestion is experiencing a transition fromwaste treatment to energy and material supply technology. Thisopens plenty of new opportunities.

doi:10.1016/j.jbiotec.2010.08.192

[I.15]

Recirculating biosurfactant foam stripper for integration withindustrial fermenters

J.B. Winterburn 1,∗, P.J. Martin 1, A.B. Russell 2

1 The University of Manchester, United Kingdom2 Unilever R&D, United KingdomKeywords: Biosurfactant; Foam fractionation; Enrichment ratio;Separation

Microbially produced biosurfactants are capable of fulfillingmany of the roles for which petrochemical or oleochemical sur-factants are currently used. They also have unique properties thatcan be utilised in innovative ways, including the improvement ofaerated foods and controlled drug delivery (Chen et al., 2006; Coxet al., 2009). Typically biosurfactants are expressed into the culturemedium, the presence of the extracellular product making suchsystems susceptible to problematic foaming. One common methodof foam control is adding antifoaming agents to the growth media(Desai and Banat, 1997). However using antifoam increases pro-duction costs and introduces a further component to be removedby downstream separation processes, which can make up 60% ofthe total production cost (Haas Jimoh Akanbi et al., 2010).

Figure 1. Apparatus for integrated biosurfactant production and separation.

We present a novel method for integrating biosurfactant pro-duction with a foam separation process. Foam fractionation isa separation technique which enriches surfactant solutions viaabsorbance to a gas liquid interface. A rising foam can be formedfrom which the liquid content drains over time, resulting in a drierand hence enriched foamate being collected. Previous results showthat enrichments in the range 10–25 can be obtained (Junker, 2007).

Foam fractionation is integrated as a parallel unit operation,connected to the fermenter via inlet and outlet ports, Figure 1.In contrast previous methodologies mounted the foam column onthe fermenter headplate (Martin et al., submitted). Biosurfactantis stripped from the culture medium as it is produced, minimis-ing the propensity of the system to foam. Process parameters havebeen varied independently, allowing the aeration rate of the fer-menter to be optimised according to the microorganisms’ oxygendemand and the foam column gas flow rate chosen to give optimumenrichment at a desired superficial gas velocity.

The successful scale up of the new production method will allowbiosurfactants to be produced efficiently by minimising undesir-able foaming in the fermenter vessel and reducing the cost offurther downstream processing through reduction of the total vol-ume of material being processed.

References

Chen, C.Y., Baker, S.C., Darton, R.C., 2006. Batch production of biosurfactant withfoam fractionation. Journal of Chemical Technology and Biotechnology. 81 (12),1923–1931.

Cox, A.R., Aldred, D.L., Russell, A.B., 2009. Exceptional stability of food foams usingclass II hydrophobin HFBII. Food Hydrocolloids. 23 (2), 366–376.

Desai, J.D., Banat, I.M., 1997. Microbial production of surfactants and their commer-cial potential. Microbiology and Molecular Biology Reviews. 61 (1), 47–64.

Haas Jimoh Akanbi, M., Post, E., Meter-Arkema, A., Rink, R., Robillard, G.T., Wang, X.,Wösten, H.A.B., Scholtmeijer, K., 2010. Use of hydrophobins in formulation ofwater insoluble drugs for oral administration. Colloids and Surfaces B: Biointer-faces. 75 (2), 526–531.

Junker, B., 2007. Foam and its mitigation in fermentation systems. BiotechnologyProgress. 23 (4), 767–784.

Martin, P. J., Dutton, H. M., Winterburn, J. B., Baker, S. and Russell, A.B. Foam frac-tionation with reflux. Chemical Engineering Science. Submitted for publication.

doi:10.1016/j.jbiotec.2010.08.193