Biobased carbon content of resin extracted from polyethylene composite by carbon-14 concentration measurements using accelerator mass spectrometry
An estimation procedure for biobased carbon content of polyethylene composite was studied using carbon-14 (14C) concentration ratios as measured by accelerated mass spectrometry (AMS). Prior to the measurement, additives and fillers in composites should be removed because they often contain a large amount of biobased carbon and may shift the estimation. Samples of resin with purity suitable for measurement were isolated from composites with a Soxhlet extractor using heated cyclohexanone. After cooling of extraction solutions, the resin was recovered as a fine semi-crystalline precipitate, which was easily filtered. Recovery rates were almost identical (99%), even for low-density polyethylene and linear low-density polyethylene, which may have lower crystallinity. This procedure could provide a suitable approach for estimation of biobased carbon content by AMS on the basis of the standard ASTM D 6866. The biobased carbon content for resin extracted from polyethylene composites allow for the calculation of biosynthetic polymer content, which is an indicator of mass percentage of the biobased plastic resin in the composite.
Biobased Contents of Natural Rubber Model Compound and Its Separated Constituents
Production of rubber products with biobased constituents from biomass resources is desirable for conserving our planet’s limited resources and preventing global warming. Herein, a natural rubber model compound was produced to determine the biobased contents as per various indices for calculating the amount of biomass resources used in rubber products. The biobased mass and biobased carbon contents of the natural rubber model compound were 38.7% and 39.2%, respectively, which were calculated from the feed amounts of the constituents as per the International Organization for Standardization (ISO)/the draft of International Standard (DIS) 16620-2 and 16620-4. The model compound was separated into its constituents such as polymer, additive, carbon black, and zinc oxide using ISO 1407, 4650, 7720-2, and 9924-3. The biobased carbon content of this model compound was 37.6%, calculated from the percent of modern carbon (pMC), which was measured directly using accelerator mass spectrometry (AMS). The calculated values for this model compound agreed with those calculated from the feed amounts of the constituents. Thus, it was confirmed that these calculation and determination methods of the biobased mass and the biobased carbon contents for rubber products should be published as new ISO international standards after a discussion at technical committee 45, “rubber and rubber products” to evaluate rubber products with larger biobased contents of natural rubber and other biobased ingredients.
Effect of Aeration and Agitation Regimes on Lipase Production by Newly Isolated Rhodotorula mucilaginosa–MTCC 8737 in Stirred Tank Reactor Using Molasses as Sole Production Medium
The influence of media and process parameters (aeration and agitation) on fermentation broth rheology and biomass formation has been studied in 1.5-l stirred tank reactor for lipase production using Rhodotorula mucilaginosa MTCC 8737. Molasses, as sole production medium, is used for lipase production by varying aeration (1, 2, and 3 vvm) and agitation speeds (100, 200, and 300 rpm). Maximum lipase activity of 72 U/ml was obtained during 96 h of fermentation at 2 vvm, 200 rpm, pH 7, and 25 ± 2°C temperature. Lipase production kinetics with respect to dry cell weight of biomass showed YP/S of 25.71 U/mg, specific product formation of 10.9 U/mg DC, and YX/S 2.35 mg/mg. Maximum lipase activity (MC 2) of 56 U/ml was observed at 1% molasses, and a further increase in the molasses concentration of (%) 1.5 and 2 inhibited the product formation of lipase with 15 and 8.5 U/ml, respectively. The production kinetics of molasses media showed YP/X was 14 U/mg DC, YP/S 16 U/mg, and YX/S 1.14 mg/mg during 96 h of bioreactor operation. The kLa values for all batches (MC 1–MC 4) at 96 h of fermentation were 32, 28, 21, and 19/h, and the |oxygen transfer rate were 54.4, 56, 35.7, and 17.29 mg/l h, respectively. Increase in molasses concentration resulted in decreased lipase activity by increase in viscosity of the fermentation broth.