Molasses as a carbon source

Figure 3. Mean urea hydrolysis rates for Snake River Plain Aquifer groundwater consortia provided with 0 (GW), 0.01%, 0.001%, and 0.00075% molasses as a carbon source supplement along with 5.9 nmol C-urea. For comparison, mean urea hydrolysis rates are also shown for B. pasteurii, E. coli, and filtered groundwater, all with 0.001% molasses. Each treatment was performed in triplicate, and error bars depict the standard deviation.

Growth media for bacteria are simple and composed of cheap materials (e.g. molasses as a carbon source). 

Bhushan and Joshi (2006) used apple pomace extract as a carbon source in an aerobic-fed batch culture for the production of baker s yeast. The fermentable sugar concentration in the bioreactor was regulated at 1-2%, and a biomass yield of 0.48 g/g of sugar was obtained. Interestingly, the dough-raising capacity of the baker s yeast grown on the apple pomace extract was apparently the same as that of commercial yeast. The use of apple pomace extract as substrate is a useful alternative to molasses, traditionally used as a carbon source for baker s yeast production. 

Initially sugars were used extensively for the production of lA. However, using sugars as a carbon source is very expensive for industrial levels of production, which demand economically feasible substrates, such as starch, molasses, wood, or corn syrup hydrolyzates and other combinations (Klement et al., 2012 Klement and Biichs, 2013 Sieker et al., 2012). Nevertheless, beet or sugarcane molasses are the most commonly used carbon sources (Nubel and Ratajak, 1964), which are pretreated by ion exchange or ferrocyanide and subsequently used for fermentation (Bath and Schweiger, 1963). Apart from these, other varieties of... 

It has been accounted that, on a production scale of PHB of 100,000 tons per year, the production costs will decrease from US 4.91 to US 3.72 kg , if hydrolysed com starch (US 0.22 kg ) is chosen as the carbon source instead of glucose (US 0.5 kg ) [33]. But this is still far beyond the cost for conventional polymers, which in 1995 was less than US 1 [32]. Lee et al. estimated that PHB and mcI-PHA can be produced at a cost of approximately US 2 kg [36]. The precondition therefore would be attaining high productivity and the use of inexpensive carbon sources. Among such substrates, molasses [37], starch [38], whey from the dairy industry [37-42], surplus glycerol from biodiesel production [39, 43], xylose [44, 45], and plant oils [46] are available. 

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. 

In Japan Chlorella spp has been produced for food in continuous aseptic systems in conventional bioreactors. The organisms are grown in the dark as heterotrophs using sucrose (in the form of molasses) or glucose as carbon and energy source. Production has been 2,000-3,000 tonnes per year at a selling price of (US)10-22 kg 1 (1990 prices). This product is sold as a high-value health food. 

As for the cultivation of other types of marine microorganisms, e.g., those with a specific potential for the production of biologically active metabolites, predominantly small-scale experiments (shake flasks) have been described. Alternatively, artificial seawater or 25 50 75 90% natural seawater has served as a basis for nutrient media. The concentrations of carbon and nitrogen sources reached up to 2 % (w/w) starch, glucose, molasses, glycerol, soybean oil, yeast extract, malt extract, beef extract, peptone, cornsteep liquor and NZ-amine. In the absence of artificial or natural seawater, high concentrations of... 

---