Synthesis and characterization of hindered‐phenol‐containing amine moieties as antioxidants for polypropylene copolymers

(4‐Ethylphenyl)‐3,5‐ditertiarybutyl‐4‐hydroxybenzylamine, 1‐phenyl‐4‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperazine, and 1‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperidine were synthesized and characterized, and their performance in polypropylene copolymer (PPCP) was tested by multiple extrusions in a Brabender plasticorder. The thermooxidative stability of PPCP was assessed by the measurement of oxidative induction time at 200 ± 1°C, and the thermal stability was assessed by observation of the change in the melt flow rate. A comparative study of the synthesized antioxidants with the commercially available antioxidant 2,6‐ditertiarybutyl‐4‐methylphenol was made. The presence of phenolic and amino groups influenced the performance of the antioxidants. The performance of the antioxidants influenced the thermal stability of the PPCP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1097–1103, 2004     

Impact of low lignin containing brown midrib sorghum mutants to harness biohydrogen production using mixed anaerobic consortia

Three low lignin containing bmr 3 derivatives, namely DRT 07K1, DRT 07K6 and DRT 07K15 developed through backcrossing were used along with the parent, bmr 3 source mutant (IS 21888) for evaluation of biohydrogen production. Results demonstrated that biohydrogen production varied amongst bmr derivatives under similar fermentation conditions. Significant negative correlation was observed between lignin content and fermentative biohydrogen production. All bmr derivatives with lower lignin content produced higher levels of biohydrogen compared to source bmr 3 (IS 21888) which has more lignin content. The maximum and a minimum biohydrogen production observed was 72 and 50 ml/g Total Volatile Solids (TVS) for the DRT 07K6 bmr3 derivative and bmr 3 (IS 21888) respectively. Acetate and butyrate were accounted >85% of volatile fatty acids, indicating acid type fermentations. Statistical analysis revealed that all bmr mutant derivatives with respect to source differ significantly in cumulative biohydrogen production, plant height, grain yield and lignin content. Biohydrogen production from biomass associated at least two different levels, one at lignin entanglement another at the polymeric nature of cellulose and hemicellulose. Further studies are necessary to determine the effect of biomass structure associated with different bmr traits on the microbial growth and biohydrogen production rate.     

Influence of linoleic acid,pH and HRT on anaerobic microbial populations and metabolic shifts in ASBRs during dark hydrogen fermentation of lignocellulosic sugars

In this study, controlling an anaerobic microbial community to increase the hydrogen (H₂) yield during the degradation of lignocelluosic sugars was accomplished by adding linoleic acid (LA) at low pH and reducing the hydraulic retention time (HRT) of an anaerobic sequencing batch reactor (ASBR). At pH 5.5 and a 1.7 d HRT, the maximum H₂ yield for LA treated cultures fed glucose or xylose reached 2.89 ± 0.18 mol mol⁻¹ and 1.94 ± 0.17 mol mol⁻¹, respectively. The major soluble metabolites at pH 5.5 with a 1.7 day HRT differed between the control and LA treated cultures. A metabolic shift toward H₂ production resulted in increased hydrogenase activity in both the xylose (13%) and glucose (34%) fed LA treated cultures relative to the controls. In addition, the Clostridia population and the H₂ yield were elevated in cultures treated with LA. A flux balance analysis for the LA treated cultures showed a reduction in homoacetogenic activity which was associated with reducing the Bacteriodes levels from 12% to 5% in the glucose fed cultures and 16% to 10% in the xylose fed cultures. Strategies for controlling the homoacetogens and optimal hydrogen production from glucose and xylose are proposed.     

Fermentative biohydrogen production by mixed anaerobic consortia: Impact of glucose to xylose ratio

Glucose and xylose are the dominant monomeric carbohydrates present in agricultural materials which can be used as potential building blocks for various biotechnological products including biofuels production. Hence, the imperative role of glucose to xylose ratio on fermentative biohydrogen production by mixed anaerobic consortia was investigated. Microbial catabolic H₂ and VFA production studies revealed that xylose is a preferred carbon source compared to glucose when used individually. A maximum of 1550 and 1650 ml of cumulative H₂ production was observed with supplementation of glucose and xylose at a concentration of 5.5 and 5.0 g L⁻¹, respectively. A triphasic pattern of H₂ production was observed only with studied xylose concentration range. pH impact data revealed effective H₂ production at pH 6.0 and 6.5 with xylose and glucose as carbon sources, respectively. Co-substrate related biohydrogen fermentation studies indicated that glucose to xylose ratio influence H₂ and as well as VFA production. An optimum cumulative H₂ production of 1900 ml for 5 g L⁻¹ substrate was noticed with fermentation medium supplemented with glucose to xylose ratio of 2:3 at pH 6. Overall, biohydrogen producing microbial consortia developed from buffalo dung could be more effective for H₂ production from lignocellulosic hydrolysates however; maintenance of glucose to xylose ratio, inoculum concentration and medium pH would be essential requirements.     

Biohydrogen production from renewable agri-waste blend: Optimization using mixer design

Biohydrogen from untreated mixed renewable agri-waste using buffalo dung compost is reported. Corn husk (CH) supported 25% higher hydrogen (H₂) production and showed the maximum value (62.38%) with p value (1.2 × 10⁻⁶) revealing its significance at individual and interactive level, respectively, compared to ground nut shell (GNS) and rice husk (RH). Augmented-simplex-lattice design experimentation revealed that a partial supplementation of RH or GNS to CH improves H₂ yield. Multiple-linear-regression analysis indicated that a quadratic model (low p = 0.0023, high F value = 35.99 and R²_quadratic = 0.99) was more significant compared to other (linear, cubic and special cubic) models. Acetate and butyrate were accounted >80% of the volatile fatty acids (VFAs). A maximum accumulation of 65.78 ml H₂ g⁻¹ TVS was produced using agri-wastes in the ratio of CH:RH:GNS = 70:16:12.