Renewable carbon substrates

Ogunjobi, A. A., Ogundele, A. O., Fagade, O. E. Production of polyhydroxyalkanoates by Pseudomonas putrefaciens from cheap and renewable carbon substrates. Electron J Environ Agr Food Chem 2011, 10,2806-2815. 

Wang et al. [34] have introduced a new heated mercury film electrode based on a screen printed carbon substrate. It was used in anodic stripping and exhibited a significantly improved signal-to-noise ratio. A directly heated mercury film electrode for anodic stripping voltammetry has been described by Jasinski [35]. Different factors influencing the quality of analytical determination have been investigated. Renewed mercury electrodes and examples of their various applications have been reviewed in Ref. 36. Lovric and Scholz [37] have discussed the conditions... 

Plant oils or their derived fatty acids are inexpensive renewable carbon sources. In addition, the theoretical yield coefficient of bioproducts (PHA) from plant oil and fatty acid is considerably higher than that from sugars. High cell density fed-batch cultures produced value-added products from soybean oil or oleic acid as the carbon source. PHAs with high yield were produced by fed-batch culture of R. eutropha or its recombinant strain from soybean oil. High cell concentrations obtained by fed-batch cultures from oleic acid improved lipase activity by C. cylindracea and 10-KSA by Flavobacterium, sp. DS5, compared with those of flask cultures. There are still many industrially important value-added products that can be produced from inexpensive substrates such as soybean oil. 

The ready availability of starch-based industrial wastes and their renewable nature merit their use as substrates for poly-betahydroxybutyrate (PHB) production from activated sludge. This would not only utilize the excess sludge generated and reduce the load on landfills, but would also contribute to reduction in the cost of PHB production by avoiding sterile conditions and pure carbon sources for maintenance and growth of pure cultures. PHB content is the most important factor affecting the production cost of PHB due to its effect on PHB yield and recovery efficiency, followed by cultural conditions and carbon substrates used (Khardenavis, 2007). 

Renewable resources, like industrial wastes/by-products such as glycerol, whey, molasses, hydrocarbon residue, and CO2 can be used as carbon substrates. 

With an aim to develop cost-competitive bio-based SA production processes from renewable non-food biomass, three important parameters, that is, productivity, titer, and yield, that affect the economic competitiveness of the bioprocess need to be considered. Productivity determines the size offermentor and other process equipment, and thus high productivity reduces the direct fixed capital costs, and also operating costs through the reduced depreciation costs of the equipment. However, the titer (concentration) cannot be sacrificed too much to increase the productivity because a low titer will significantly increase the recovery costs. Yield is very important for commodity chemicals including SA because it affects the costs of raw material (carbon substrate). 

A major limiting factor in the development of biodegradable polyesters is the expense of the carbon substrate used in the fermentation, which can account for up to 50 % of the overall production cost of PHAs (14,15,16,17). Production based on relatively inexpensive renewable substrates, including the variety of carbon feedstocks available in underutilized agricultural, forestry, and food wastes, could make PHA-derived thermoplastics more competitive with plastic products derived from future dwindling petroleum reserves. Reductions in the overall cost of production could be attained by utilization of the hemicellulosic... 

The worldwide research is advancing focused on the use of renewable raw materials as carbon substrates as well as nutrient additive resources. In this context, there is a strong interest to reduce costs for raw materials and to use renewable resources. 

If a fermentation process is used for PHA synthesis this problem can partially be overcome by using cheap surplus and waste materials as renewable carbon sources (e.g. molasses, whey, cellulose hydrolysate) or other cheap carbon sources from fossil resources like methanol derived from natural gas, because roughly 50% of the total production costs derive from the carbon source costs. Unfortunately many of the well known production strains can not be used for PHA production from such substrates, because these microbial strains show either low yields or low production rates, when they grow on these substrates, or they simply cannot utilize these carbon sources at all. These drawbacks can be overcome either by isolating new microbial strains or by applying genetically modified strains for the production process. 

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