Effect of partially hydrolyzed polyacrylamide (HPAM) on the bacterial communities of wetland rhizosphere soils and their efficiency in HPAM and alkane degradation.

The effect of partially hydrolyzed polyacrylamide (HPAM) on structure and function of rhizosphere soil bacterial communities in constructed wetlands has been largely underinvestigated. In this study, we compare the effect of 250, 500, and 1000 mg/L of HPAM on bacterial community composition of Phragmites australis associated rhizosphere soils in an experimental wetland using MiSeq amplicon sequencing. Rhizosphere soils from the HPAM-free and the 500-mg/L-exposed treatments were used for laboratory experiments to further investigate the effect of HPAM on the soil's degradation and respiration activities. Soils treated with HPAM showed differences in bacterial communities with the dominance of Proteobacteria and the enrichment of potential hydrocarbon and HPAM-degrading bacteria. CO2 generation was higher in the HPAM-free soils than in the HPAM pre-exposed soil, with a noticeable increase in both soils when oil was added. The addition of HPAM at different concentrations had a more pronounced effect on CO2 evolution in the HPAM-pre-exposed soil. Soils were able to degrade between 37 ± 18.0 and 66 ± 6.7% of C10 to C30 alkanes after 28 days, except in the case of HPAM-pre-exposed soil treated with 500 mg/L where degradation reached 92 ± 4.3%. Both soils reduced HPAM concentration by 60 ± 15% of the initial amount in the 500 mg/L treatment, but by only ≤ 21 ± 7% in the 250-mg/L and 1000-mg/L treatments. In conclusion, the rhizosphere soils demonstrated the ability to adapt and retain their ability to degrade hydrocarbon in the presence of HPAM.

Waste office paper: A potential feedstock for cellulase production by a novel strain Bacillus velezensis ASN1.

This paper reports the cellulase (FPase) production by newly isolated Bacillus velezensis ASN1 using waste office paper (WOP) as feedstock and optimization of production conditions through two level factorial design, steepest ascent/descent and second order response surface methodology (RSM). Various fermentation parameters, like chemical factors (potassium dihydrogen phosphate, potassium chloride, yeast extract, magnesium sulphate, sodium nitrate, Tween 80, and waste office paper), physical factors (temperature, pH and time) and biological factor (inoculum size) were examined using two level full factorial design to check the key factors significantly affecting the cellulase production. The central composite design (CCD) was used to optimize the vital fermentation parameters, such as carbon (WOP), nitrogen, pH, and inoculum concentration in the medium for achieving higher cellulase production. The optimum medium composition was found to be WOP (9 g/L), sodium nitrate (0.35 g/L), inoculum size (6.56%) and pH 4.72. The model prediction of 2.46 U/mL cellulase activity at optimum conditions was verified experimentally as 2.42 U/mL.

Biorefinery production of poly-3-hydroxybutyrate using waste office paper hydrolysate as feedstock for microbial fermentation.

Waste paper, a major fraction of municipal solid waste, has a potential to serve as renewable feedstock for the biorefineries of fuels, chemicals and materials due to rich in cellulose and abundant at low cost. This study evaluates the possibility of waste office paper (WOP) to serve as a potential feedstock for the biorefinery production of poly (3-hydroxybutyrate). In this study, the WOP was pretreated, enzymatically saccharified and the hydrolysate was used for PHB production. The hydrolysate mainly consists of glucose (22.70g/L) and xylose (1.78g/L) and the corresponding sugar yield was about 816mg/g. Ammonium sulphate and C/N ratio 20 were identified as most favorable for high yield of PHB. The batch fermentation of Cupriavidus necator using the pretreated WOP hydrolysate resulted in cell biomass, PHB production and PHB content of 7.74g/L, 4.45g/L and 57.52%, respectively. The volumetric productivity and yield achieved were 0.061g/L/h and 0.210g/g sugar, respectively. The results suggested that WOP could be a potential alternative feedstock for the biorefinery production of bioplastics.