Value-Added Products from Lignocellulosic Agricultural Residues

An alternative to the complex pretreatment and hydrolysis of lignocellulosic material for submerged fermentation is to use biomass with minimal pretreatment in a Solid State Fermentation (SSF) process. Advantages of SSF are: utilization of an otherwise unusable carbon source, low energy demand, high volume productivity, natural fungal environment, lower sterility requirements, minimal metabolic bottlenecks, low water demand and reduced wastewater issues.

The major challenges facing SSF today are reactor design and engineering, monitoring and process control aspects and scale-up issues of temperature, pH, O2, substrate and moisture gradients. The activities integrate highly efficient bioreactor systems with high-yielding biocatalysts to create substantial value.

Chemostat Technology Development

One of the significant inefficiencies in bioprocess research is the requirement for a large number of repetitive experiments using batch fermentation technology in which only one variable can be examined in each experiment. Alternatively, by using continuous culture technology (chemostat) industrial biotechnology research is accelerated. Optimization experiments using variable operating conditions can be performed rapidly. The chemostat offers an efficient method to evaluate substrate changes.

Respiratory Quotient (RQ) as a Bio-product Optimization Tool

A large focus in bio-product optimization is the delivery of oxygen, both as a micro-nutrient and as an important regulator of metabolic pathways. The respiratory quotient (RQ), the ratio of the carbon dioxide evolution rate (mol/m3.hr) to the oxygen uptake rate (mol/m3.hr) is an indicator of the metabolic state of the microbe. The RQ is a variable that is independent of both biomass concentration and process scale. Furthermore, it can be used as a diagnostic tool or in industrial applications where the inlet oxygen composition is manipulated using a PID controller with the proportional gain as a function of the RQ set-point.