The rapidly expanding market for biodiesel has increased the supply and reduced the cost of glycerol, making it an attractive sustainable feed stock for the fuel and chemical industry. Glycerol-based biorefinery is the microbial fermentation of crude glycerol to produce fuels and chemicals. A major challenge is to obtain microbes tolerant to inhibitors such as salts and organic solvents present in crude glycerol. Microbial screening was attempted to isolate novel strain capable of growing on crude glycerol as a sole carbon source. The newly isolated bacteria, identified as nonpathogenic Kluyvera cryocrescens S26 could convert biodiesel-derived crude glycerol to ethanol with high yield and productivity. The supplementation of nutrients such as yeast extract resulted in distinguished enhancement in cell growth as well as ethanol productivity under anaerobic condition. When glycerol fermentation is performed under microaerobic condition, there is also a remarkable improvement in cell growth, ethanol productivity and yield, compared with those under strict anaerobic condition. In batch fermentation under microaerobic condition, K. cryocrescens S26 produced 27 g/l of ethanol from crude glycerol with high molar yield of 80% and productivity of 0.61 g/l/h.
Black phosphorus, or BP, has found a lot of applications in recent years including photonics. The most recent studies have shown that the material has an excellent optical nonlinearity useful in many areas, one of which is in saturable absorption for passive mode‐locking. A direct interaction scheme for mode‐locking, however, has a potential to optically cause permanent damage to the already delicate material. Evanescent field interaction scheme has already been proven to be a useful method to prevent such danger for other 2‐dimensional nanomaterials. In this report, we have utilized the evanescent field interaction to demonstrate that the optical nonlinear characteristics of BP is sufficiently strong to use in such an indirect interaction method. The successful demonstration of the passive mode‐locking operation has generated pulses with the pulse duration, repetition rate, and time bandwidth product of 2.18 ps, 15.59 MHz, and 0.336, respectively.
The rapidly expanding market for bioethanol and biodiesel is remarkably altering the cost and availability of glycerol. In general, approximately 10 pounds of crude glycerol are formed for every 100 pounds of biodiesel produced. Bioethanol process also generates glycerol up to 10% (w/w) of the total sugar consumed as a byproduct. Crude glycerol has thus been widely recognized as an attractive sustainable resource for chemical industries. Glycerol-based biorefinery is the microbial fermentation processes using inexpensive and readily available glycerol as the raw material to produce fuels and chemicals. A major challenge in fermentation of the low-grade crude glycerol is to obtain microbial strains tolerant to undesirable inhibitory components such as salts and organic solvents that present in crude glycerol. There have been several attempts to explore anaerobic microbial assimilation of glycerol using reconstructed microbial systems via microbial screening and metabolic pathway engineering. As a result, fuels as well as some high-value products were found to be produced by microbial fermentation of glycerol. This review describes biological processes using glycerol that produce fuels and chemicals including 1,3-propanediol, ethanol and organic acids.
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