Supercritical CO2 Extraction of Bioactive Compounds from Mango (Mangifera indica L.) Peel and Pulp.

The potential of supercritical CO2 (SC-CO2) for the extraction of bioactive compounds from mango by-products was assessed. Carotenoid extraction was optimized using a design of experiments based on temperature (35, 55 and 70 °C), pressure (10 and 35 MPa) and co-solvent addition (0%, 10% and 20% of ethanol or acetone). Moreover, the co-extraction of phenolic acids, flavonoids and xanthonoids was evaluated in a subset of parameters. Finally, a comparison was made between SC-CO2 and a two-step organic solvent extraction of the bioactive compounds from the pulp and peel fractions of two Ecuadorian varieties. The optimal extraction temperature was found to be dependent on the bioactive type, with phenolics requiring higher temperature than carotenoids. The optimal overall conditions, focused on maximal carotenoids recovery, were found to be 55 °C, 35 MPa and 20% of ethanol. The main carotenoid was ß-carotene, while phenolics differed among the varieties. The bioactive content of the peel was up to 4.1-fold higher than in the pulp fraction. Higher antioxidant activity was found in the extracts obtained with organic solvents. SC-CO2 is a promising technology for the isolation of valuable compounds from mango by-products.

Characteristics of chitin extracted from black soldier fly in different life stages.

Chitin was collected and extracted along different lifecycle stages of the Black Soldier Fly (BSF) (larvae, prepupae, pupae, flies, shedding & cocoons). The chitin content in the collected biomass ranged between 8% and 24%, with sheddings and cocoons being most rich in chitin. Purified chitin was subjected to a physicochemical evaluation based on FTIR, XRD, and TGA as well as a deacetylation step. The data indicated that BSF chitin was α-chitin with FTIR profiles matching closely to shrimp chitin and showing some differences compared to squid pen chitin (ß-chitin). Small physicochemical differences were observed among the different BSF samples. Prepupae and cocoon chitin was more crystalline while chitin from larvae and sheddings had a lower thermal degradation temperature. In addition, sheddings were more difficult to purify. Further processing to chitosan showed that a deacetylation degree of 89% could be obtained for all samples after 3 h, although sheddings were found to be less reactive in the deacetylation process. Overall, the small differences in physicochemical properties that were detected between the BSF chitin samples did not prevent further processing of chitin to chitosan with the same degree of deacetylation via the same treatment.

Biobutanol production from C5/C6 carbohydrates integrated with pervaporation: experimental results and conceptual plant design.

In this study, a simulated lignocellulosic hydrolyzate was used in a continuous two-stage fermentor setup for production of acetone, butanol and ethanol. An organophilic pervaporation unit was coupled to the second fermentor. The dilution rate in the first fermentor was kept constant at 0.109 h(-1), while the dilution rate in the second fermentor was gradually decreased from 0.056 to 0.020 h(-1). Glucose was completely consumed, while 61% of the xylose was consumed at the lowest dilution rate, leading to an overall solvent productivity of 0.65 g L(-1) h(-1) and a high concentration of 185 g kg(-1) solvents in the permeate in the last fermentation zone during 192 h. Based on the experimental results, a process integrated with organophilic pervaporation was conceptually designed and compared with a base-case. Chemcad simulations indicate an energy reduction of ~50% when organophilic pervaporation is used. This study also demonstrates significant reductions in process flows and energy consumption by the use of organophilic pervaporation as in situ product recovery technology.

Field assessment of guar gum stabilized microscale zerovalent iron particles for in-situ remediation of 1,1,1-trichloroethane.

A pilot injection test with guar gum stabilized microscale zerovalent iron (mZVI) particles was performed at test site V (Belgium) where different chlorinated aliphatic hydrocarbons (CAHs) were present as pollutants in the subsurface. One hundred kilograms of 56µm-diameter mZVI (~70gL(-1)) was suspended in 1.5m(3) of guar gum (~7gL(-1)) solution and injected into the test area. In order to deliver the guar gum stabilized mZVI slurry, one direct push bottom-up injection (Geoprobe) was performed with injections at 5 depths between 10.5 and 8.5m bgs. The direct push technique was preferred above others (e.g. injection at low flow rate via screened wells) because of the limited hydraulic conductivity of the aquifer, and to the large size of the mZVI particles. A final heterogeneous distribution of the mZVI in the porous medium was observed explicable by preferential flow paths created during the high pressure injection. The maximum observed delivery distance was 2.5m. A significant decrease in 1,1,1-TCA concentrations was observed in close vicinity of spots where the highest concentration of mZVI was observed. Carbon stable isotope analysis (CSIA) yielded information on the success of the abiotic degradation of 1,1,1-TCA and indicated a heterogeneous spatio-temporal pattern of degradation. Finally, the obtained results show that mZVI slurries stabilized by guar gum can be prepared at pilot scale and directly injected into low permeable aquifers, indicating a significant removal of 1,1,1-TCA.

Differential responses of eubacterial, Mycobacterium, and Sphingomonas communities in polycyclic aromatic hydrocarbon (PAH)-contaminated soil to artificially induced changes in PAH profile.

Recent reports suggest that Mycobacterium is better adapted to soils containing poorly bioavailable polycyclic aromatic hydrocarbons (PAHs) compared to Sphingomonas. To study this hypothesis, artificial conditions regarding PAH profile and PAH bioavailability were induced in two PAH-contaminated soils and the response of the eubacterial, Mycobacterium, and Sphingomonas communities to these changed conditions was monitored during laboratory incubation. Soil K3663 with a relatively high proportion of high molecular weight PAHs was amended with phenanthrene or pyrene to artificially change the soil into a soil with a relatively increased bioavailable PAH contamination. Soil AndE with a relatively high proportion of bioavailable low molecular weight PAHs was treated by a single-step Tenax extraction to remove the largest part of the easily bioavailable PAH contamination. In soil K3663, the added phenanthrene or pyrene compounds were rapidly degraded, concomitant with a significant increase in the number of phenanthrene and pyrene degraders, and minor and no changes in the Mycobacterium community and Sphingomonas community, respectively. However, a transient change in the eubacterial community related to the proliferation of several gamma-proteobacteria was noted in the phenanthrene-amended soil. In the extracted AndE soil, the Sphingomonas community initially developed into a more diverse community but finally decreased in size below the detection limit. Mycobacterium in that soil never increased to a detectable size, while the eubacterial community became dominated by a gamma-proteobacterial population. The results suggest that the relative bioavailability of PAH contamination in soil affects bacterial community structure but that the behavior of Mycobacterium and Sphingomonas in soil is more complex than prospected from studies on their ecology and physiology.

Characterization of cultures enriched from acidic polycyclic aromatic hydrocarbon-contaminated soil for growth on pyrene at low pH.

Two polycyclic aromatic hydrocarbon (PAH)-contaminated soils of pH 2 were successfully used as inoculum to enrich cultures growing on phenanthrene and pyrene at different pHs, including pH 3. Selected pyrene-utilizing cultures obtained at pH 3, pH 5, and pH 7 were further characterized. All showed rapid [14C]pyrene mineralization at pH 3 and pH 5 and grew on pyrene at pH values ranging from 2 to 6. Eubacterial and mycobacterial 16S rRNA gene denaturing gradient gel electrophoresis fingerprinting and sequencing indicated that the cultures were dominated by a single bacterium closely related to Mycobacterium montefiorense, belonging to the slow-growing Mycobacterium sp. In contrast, a culture enriched on pyrene at pH 7 from a slightly alkaline soil sampled at the same site was dominated by Pseudomonas putida and a fast-growing Mycobacterium sp. The M. montefiorense-related species dominating the pyrene-utilizing cultures enriched from the acidic soils was also the dominant Mycobacterium species in the acidic soils. Our data indicate that a slow-growing Mycobacterium species is involved in PAH degradation in that culture and show that bacteria able to degrade high-molecular-weight PAHs at low pH are present in acidic PAH-contaminated soil.

Distribution of the Mycobacterium community and polycyclic aromatic hydrocarbons (PAHs) among different size fractions of a long-term PAH-contaminated soil.

Summary Mycobacterium is often isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soil as degraders of PAHs. In model systems, Mycobacterium shows attachment to the PAH substrate source, which is considered to be a particular adaptation to low bioavailability as it results into increased substrate flux to the degraders. To examine whether PAH-degrading Mycobacterium in real PAH-contaminated soils, in analogy with model systems, are preferentially associated with PAH-enriched soil particles, the distribution of PAHs, of the PAH-mineralizing capacity and of Mycobacterium over different fractions of a soil with an aged PAH contamination was investigated. The clay fraction contained the majority of the PAHs and showed immediate pyrene- and phenanthrene-mineralizing activity upon addition of (14)C-labelled pyrene or phenanthrene. In contrast, the sand and silt fractions showed a lag time of 15-26 h for phenanthrene and 3-6 days for pyrene mineralization. The maximum pyrene and phenanthrene mineralization rates of the clay fraction expressed per gram fraction were three to six times higher than those of the sand and silt fractions. Most-probable-number (MPN)-polymerase chain reaction demonstrated that Mycobacterium represented about 10% of the eubacteria in the clay fraction, while this was only about 0.1% in the sand and silt fractions, indicating accumulation of Mycobacterium in the PAH-enriched clay fraction. The Mycobacterium community composition in the clay fraction represented all dominant Mycobacterium populations of the bulk soil and included especially species related to Mycobacterium pyrenivorans, which was also recovered as one of the dominant species in the eubacterial communities of the bulk soil and the clay fraction. Moreover, Mycobacterium could be identified among the major culturable PAH-degrading populations in both the bulk soil and the clay fraction. The results demonstrate that PAH-degrading mycobacteria are mainly associated with the PAH-enriched clay fraction of the examined PAH-contaminated soil and hence, that also in the environmental setting of a PAH-contaminated soil, Mycobacterium might experience advantages connected to substrate source attachment.

Comparison of mineralization of solid-sorbed phenanthrene by polycyclic aromatic hydrocarbon (PAH)-degrading Mycobacterium spp. and Sphingomonas spp.

The mineralization of 14C-phenanthrene, sorbed to porous synthetic amberlite sorbents, i.e., IRC50, XAD7-HP, and XAD2, by three phenanthrene-degrading Mycobacterium soil isolates, i.e., strains VM552, VM531, and VM451 and three phenanthrene-degrading Sphingomonas soil isolates, i.e., strains LH162, EPA505 and LH227, was compared. In P-buffer and in the presence of IRC50, for all strains the maximum rate of mineralization of 14C-phenanthrene was significantly higher (1.1-1.9 ng ml(-1) h(-1)) than the initial abiotic desorption rate (0.2 ng ml(-1) h(-1)), indicating that both Mycobacterium and Sphingomonas utilize sorbed phenanthrene with a higher rate than can be explained by abiotic desorption. Because all Mycobacterium and Sphingomonas strains belonged to different species, it can be suggested that this feature is intrinsic to those genera rather than a specific feature of a particular strain. The final mineralization extent in P-buffer in the presence of IRC50 was about a factor of two higher for the Mycobacterium strains compared to the Sphingomonas strains. Moreover, a significantly higher normalized phenanthrene mineralization ratio in the presence of IRC50 to the control (without IRC50) was found for the Mycobacterium strains compared to the normalized ratio found for the Sphingomonas strains. Addition of minimal nutrients had a more beneficial effect on phenanthrene mineralization by Sphingomonas compared to Mycobacterium, resulting into similar mineralization extents and rates for both types of strains in the presence of IRC50. Our results show that Mycobacterium is better adapted to utilization of sorbed phenanthrene compared to Sphingomonas, especially in nutrient-poor conditions.