Patent ID: 8748138
Filing Date: 2014-06-10
Classification: C02F,C12P

Abstract:
1. A fed-batch method for producing high molecular weight polyhydroxyalkanoates (PHAs) in biomass, comprising: directing biomass into a reactor having at least one stimulating zone and at least one maintenance zone wherein the stimulating zone and maintenance zone are at least partially separated by a physical structure; intermittently and repeatedly stimulating the biomass respiration rate of the biomass during a PHA accumulation process by exposing at least a fraction of the biomass to an elevated substrate concentration in the at least one stimulating zone while at least a portion of the remaining biomass is exposed to substrate concentrations in the maintenance zone that are less than the average substrate concentrations in the stimulating zone; monitoring and assessing, at least indirectly, the respiration rate of the biomass in the maintenance zone where the substrate concentration therein is on average less than the substrate concentration in the stimulating zone; circulating the biomass back and forth between the stimulating zone and the maintenance zone; controlling the frequency of biomass recirculation or rate of substrate addition such that the respiration rate of the biomass in the maintenance zone does not decrease by more than 70% of the extant achievable maximum respiration rate of the biomass; retaining the biomass in the reactor until a significant level of PHA is accumulated by the biomass; harvesting PHA rich biomass from the reactor; wherein repeated exposure of the biomass to elevated substrate concentrations is achieved by directing substrate into the stimulating zones and mixing the substrate with recirculated biomass; wherein the elevated concentrations of the substrate used to repeatedly stimulate the biomass respiration rate between 10 and 1000 mg-Chemical Oxygen Demand (COD)/L; wherein the above combination of method steps provides for PHA accumulation and wherein the accumulated PHA, when separated from the biomass, includes an average molecular weight of at least 400,000 g/mole.