Bioprocess Optimisation for High Cell Density Endoinulinase Production from Recombinant Aspergillus niger.

Endoinulinase gene was expressed in recombinant Aspergillus niger for selective and high-level expression using an exponential fed-batch fermentation. The effects of the growth rate (µ), glucose feed concentration, nitrogen concentration and fungal morphology on enzyme production were evaluated. A recombinant endoinulinase with a molecular weight of 66 kDa was secreted. Endoinulinase production was growth associated at µ> 0.04 h-1, which is characteristic of the constitutive gpd promoter used for the enzyme production. The highest volumetric activity (670 U/ml) was achieved at a growth rate of 93% of µmax (0.07 h-1), while enzyme activity (506 U/ml) and biomass substrate yield (0.043 gbiomassDW/gglucose) significantly decreased at low µ (0.04 h-1). Increasing the feed concentration resulted in high biomass concentrations and viscosity, which necessitated high agitation to enhance the mixing efficiency and oxygen. However, the high agitation and low DO levels (ca. 8% of saturation) led to pellet disruption and growth in dispersed morphology. Enzyme production profiles, product (Yp/s) and biomass (Yx/s) yield coefficients were not affected by feed concentration and morphological change. The gradual increase in the concentration of nitrogen sources showed that, a nitrogen limited culture was not suitable for endoinulinase production in recombinant A. niger. Moreover, the increase in enzyme volumetric activity was still directly related to an increase in biomass concentration. An increase in nitrogen concentration, from 3.8 to 12 g/L, resulted in volumetric activity increase from 393 to 670 U/ml, but the Yp/s (10053 U/gglucose) and Yx/s (0.049 gbiomasDWs/gglucose) did not significantly change. The data demonstrated the potential of recombinant A. niger and high cell density fermentation for the development of large-scale endoinulinase production system.

A global conversation about energy from biomass: the continental conventions of the global sustainable bioenergy project.

The global sustainable bioenergy (GSB) project was formed in 2009 with the goal of providing guidance with respect to the feasibility and desirability of sustainable, bioenergy-intensive futures. Stage 1 of this project held conventions with a largely common format on each of the world's continents, was completed in 2010, and is described in this paper. Attended by over 400 persons, the five continental conventions featured presentations, breakout sessions, and drafting of resolutions that were unanimously passed by attendees. The resolutions highlight the potential of bioenergy to make a large energy supply contribution while honouring other priorities, acknowledge the breadth and complexity of bioenergy applications as well as the need to take a systemic approach, and attest to substantial intra- and inter-continental diversity with respect to needs, opportunities, constraints and current practice relevant to bioenergy. The following interim recommendations based on stage 1 GSB activities are offered: - Realize that it may be more productive, and also more correct, to view the seemingly divergent assessments of bioenergy as answers to two different questions rather than the same question. Viewed in this light, there is considerably more scope for reconciliation than might first be apparent, and it is possible to be informed rather than paralysed by divergent assessments.- Develop established and advanced bioenergy technologies such that each contributes to the other's success. That is, support and deploy in the near-term meritorious, established technologies in ways that enhance rather than impede deployment of advanced technologies, and support and deploy advanced technologies in ways that expand rather than contract opportunities for early adopters and investors.- Be clear in formulating policies what mix of objectives are being targeted, measure the results of these policies against these objectives and beware of unintended consequences.- Undertake further exploration of land efficiency levers and visions for multiply-beneficial bioenergy deployment. This should be unconstrained by current practices, since we cannot hope to achieve a sustainable and a secure future by continuing the practices that have led to the unsustainable and insecure present. It should also be approached from a global perspective, based on the best science available, and consider the diverse realities, constraints, needs and opportunities extant in different regions of the world.The future trajectory of the GSB project is also briefly considered.