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In the present study, Tween 80, a non-ionic surfactant, has been used for enhanced hydrogen production by crude glycerol bioconversion using co-culture of Enterobacter aerogenes and Clostridium butyricum . The purpose of introducing the surfactant was to decrease the crude glycerol viscosity, so that apparent solubility and bioavailability of glycerol could be improved at the expenses of pretreatment steps. Experiments were planned using central composite design (CCD); crude glycerol and Tween 80 concentrations were optimized whereas, hydrogen production, glycerol utilization and viscosity of the media were considered as responses. The response surface for quadratic model showed, Tween 80 concentration had significant effect (p < 0.05) on all the three responses. Using the optimized conditions at 17.5 g/L crude glycerol and 15 mg/L Tween 80, hydrogen production reached a maximum of 32.1 ± 0.03 mmol/L of medium. The increase in hydrogen production was around 1.25-fold in presence of Tween 80 in comparison to its absence with 25.56 ± 0.91 mmol/L production. Selected optimum conditions were also validated against absence of crude glycerol (4.69 ± 0.76), with pretreated crude glycerol (20.06 ± 0.51) and across mono-culture system (15.43 ± 0.79 to 22.14 ± 0.94). Introduction of Tween 80 to the fermentation medium improved the glycerol utilization rate, resulting in increased hydrogen production and eliminated pretreatment steps. [ABSTRACT FROM AUTHOR]

Co-substrate utilization of various wastes with complementary characteristics can provide a complete medium for higher hydrogen production. This study evaluated potential of apple pomace hydrolysate (APH) co-fermented with crude glycerol (CG) for increased H 2 production and decreased by-products formation. The central composite design (CCD) along with response surface methodology (RSM) was used as tool for optimization and 15 g/L of CG, 5 g/L of APH and 15% (v/v) inoculum were found to be optimum to produce as high as 26.07 ± 1.57 mmol H 2 /L of medium. The p -value of 0.0017 indicated that APH at lower concentration had a significant effect on H 2 production. By using CG as sole carbon source, reductive pathway of glycerol metabolism was favored with 19.46 mmol H 2 /L. However, with APH, oxidative pathway was favored with higher H 2 production (26.07 ± 1.57 mmol/L) and decrease in reduced by-products (1,3-propanediol and ethanol) formation. APH inclusion enhanced H 2 production, and decreased substrate inhibition. [ABSTRACT FROM AUTHOR]

CG (Crude glycerol) is one of the major wastes of biodiesel production process. It can be used as a substrate for lipid production by algae and the produced lipid can be recycled as a feedstock for biodiesel production. In order to avoid substrate inhibition, lipid production media are prepared by diluting the CG with distilled water. However, CG contains only a small amount of Mg (57.41 ± 18 ppm) and its concentration is further decreased to around 0.57 ppm during the dilution process. Apart from having a number of roles in algal physiology, Mg is the central atom of chlorophyll. Therefore, MgSO 4 was evaluated as a Mg source to supplement the CG based media used for lipid production by Chlorella vulgaris . By supplementing the process with 1 g/L of MgSO 4 , nearly 185.29 ± 4.53% improvement in lipid production has been achieved. Further, application of MgSO 4 nanoparticles was found to improve the lipid production by 118.23 ± 5.67%. Interestingly, unlike MgSO 4 , its nanoparticles were found to enhance the lipid production at the expense of only a small amount of glycerol. Thus, application of MgSO 4 nanoparticles could be a potential strategy for enhanced lipid yield. [ABSTRACT FROM AUTHOR]