Initial Biomass Loading Research Articles

Low-Viscosity Ether-Functionalized Ionic Liquids as Solvents for the Enhancement of Lignocellulosic Biomass Dissolution

Due to the substantial usage of fossil fuels, the utilization of lignocellulosic biomass as renewable sources for fuels and chemical production has been widely explored. The dissolution of lignocellulosic biomass in proper solvents is vital prior to the extraction of its important constituents, and ionic liquids (ILs) have been found to be efficient solvents for biomass dissolution. However, the high viscosity of ILs limits the dissolution process. Therefore, with the aim to enhance the dissolution of lignocellulosic biomass, a series of new ether-functionalized ILs with low viscosity values were synthesized and characterized. Their properties, such as density, viscosity and thermal stability, were analyzed and discussed in comparison with a common commercial IL, namely 1-butyl-3-methylimidazolium chloride (BMIMCl). The presence of the ether group in the new ILs reduces the viscosity of the ILs to some appreciable extent in comparison to BMIMCl. 1-2(methoxyethyl)-3-methylimidazolium chloride (MOE-MImCl), which possesses the lowest viscosity value among the other ether-functionalized ILs, demonstrates an ability to be a powerful solvent in the application of biomass dissolution via the sonication method. In addition, an optimization study employing response surface methodology (RSM) was carried out in order to obtain the optimum conditions for maximum dissolution of biomass in the solvents. Results suggested that the maximum biomass dissolution can be achieved by using 3 weight% of initial biomass loading with 40% amplitude of sonication at 32.23 min of sonication period.

Introducing a new salty waste for second-generation bioethanol production

ABSTRACTWe have introduced the discards of turnip juice as a raw material for bioethanol production for the first time. Pretreatment methods, initial biomass loading, and fermentation time were investigated. Supplementation of different kinds of nitrogen sources, mineral salts and agricultural waste hydrolysates were added in the growth medium. The highest bioethanol concentrations and Qp values were 7.32, 5.34, 1.55 g/L and 0.61, 0.44, 0.05 g/L.h for S. cerevisiae, K. marxianus and P. stipitis, respectively. Furthermore, Yp/s values were 0.46 g/g, 0.47 g/g, and 0.37 g/g for the three yeasts. Turnip juice discards are promising raw materials for bioethanol production.

Co-digestion of untreated macro and microalgal biomass for biohydrogen production: Impact of inoculum augmentation and microbial insights

This study assessed the co-digestion of macro and microalgal biomass towards the improvement of hydrogen production. The red macroalgal biomass (Gelidium amansii) and green mixed microalgal biomass was mixed in a ratio of 8:2, with an initial substrate concentration of 10 g/L, and various amount of inoculum addition range from 3 to 15% (v/v) was evaluated to assess the feasible substrate to inoculum ratio for the effective co-digestion of the algal biomass. The results showed that the co-digestion with 6% inoculum addition provided the peak hydrogen yield of 45 mL/g dry biomass added with a high hydrogen content of 24% in the gas phase. The other tested conditions showed moderate hydrogen content in the range of 17–22%, respectively. These results suggest that anaerobic co-digestion of macro and microalgal biomass, with appropriate initial biomass loading (6%) is essential for enhanced hydrogen production.

Biodegradation of naphthalene using a functional biomaterial based on immobilized Bacillus fusiformis (BFN)

The degradation of naphthalene using immobilized Bacillus fusiformis (BFN) strain on alginate–polyvinyl alcohol (PVA)–clays bead was much higher than that of using a freely suspended BFN strain. This was due to the beads facilitating biodegradation by enhancing concentration of naphthalene using the beads as an adsorbent in the cells’ vicinity. This was confirmed by the kinetics of naphthalene on the beads, where its adsorption onto the beads was confirmed by pseudo-second-order kinetics. The biodegradation of naphthalene fitted well to the first-order rate model. More than 99.7% of naphthalene which was removed within 12h, contained bentonite 2% (w/v), PVA 12% (w/v), alginate 0.3% (w/v) and 10% (v/v) initial biomass loading. Scanning electron microscopy (SEM) of the beads showed that B. fusiformis was evenly distributed within them. Storage stability and reusability results revealed that the ability to degrade naphthalene using beads with immobilized cells remained stable after storage at 4°C for 35 days and being reused 8 times (12 days), respectively. Furthermore the naphthalene degradation rate of immobilized cells was maintained (94.3%) at the eighth cycle.

Cholesterol oxidase production from entrapped cells ofStreptomycessp.

Production of cholesterol oxidase (COD) under batch conditions through Ca-alginate immobilized cells of Streptomyces sp. was investigated. The process was studied for optimal immobilization conditions, beads operational stability and comparisons were made with the COD production via free cells. Influence of Na-alginate concentration (1-5 g L(-1) ) and initial biomass loading on enzyme production were studied. Effects of initial pH of the production medium, temperature, shaker speed, as well as reuse of beads on the COD production were also investigated. It was observed that COD production with immobilized cells (5.6 U ml(-1) ) was higher in comparison to free cells (4.5 U ml(-1) ) under optimized conditions. The maximum COD production by free cells was observed with initial pH 7.0, rpm 200 after 96 h of incubation while immobilized cells sustain a broad pH range 6.0-9.0, rpm 300 for maximum production after 72 h. The immobilized and free cells produced maximum COD in the culture incubated at 37 and 30 °C, respectively. Other parameters bead size and Na-alginate concentration found to be optimum with 1.5 mm and 4% w/v, respectively. Scanning electron microscope study of the immobilized cells indicated that the cells in Ca-alginate beads remained in normal shape with no alterations in the morphology.

Novel pre-treatment and fractionation method for lignocellulosic biomass using ionic liquids

An efficient lignocellulosic biomass pre-treatment is a crucial step for the valorization of these kind of raw materials. Lignocellulosic biomass is a potentially valuable resource for transformation into biofuels and bio-based products. The use of ionic liquids as media for the biomass pre-treatment is an alternative method that follows the green chemistry concept. This work proposes a new methodology for wheat straw pre-treatment with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][OAc]), which allowed the production of cellulose, hemicellulose and lignin-rich fractions in a rapid and simple three-step fractionation process. Various temperatures (80–140 °C) and processing times (2–18 h) of the pre-treatment were studied. The quantitative and qualitative analysis of each lignocellulosic biomass fraction was determined by FTIR measurements. The glucan content in recovered cellulose-rich fractions was investigated by enzymatic hydrolysis. The cellulose recovery dependence on the pre-treatment conditions was ascertained through regression analysis. The optimal result for the recovery of the cellulose-rich fraction was obtained at 140 °C during 6 h achieving 37.1% (w/w) of the initial biomass loading. For the same conditions, optimal results were also produced regarding the amount of glucan present (81.1% w/wbiomass) in cellulose-rich fractions, the carbohydrate enrichment in the hemicellulose fraction (96% wt) and the purity of lignin (97% wt). The recovery of IL was performed after each pre-treatment and the obtained yields were up to 86% (w/w). The recovered ILs were analyzed by 13C and 1H NMR. The presence of value-added phenolic compounds in the recovered ILs was analyzed by capillary electrophoresis. Vanillin and its derivatives, as well as other lignin-based products, were identified.

Experimental Investigation and Artificial Neural Network-Based Modeling of Batch Reduction of Hexavalent Chromium by Immobilized Cells of Newly Isolated Strain of Chromium-Resistant Bacteria

The batch bioreduction of Cr(VI) by the cells of newly isolated chromium-resistant Acinetobacter sp. bacteria, immobilized on glass beads and Ca-alginate beads, was investigated. The rate of reduction and percentage reduction of Cr(VI) decrease with the increase in initial Cr(VI) concentration, indicating the inhibitory effect of Cr(VI). Efficiency of bioreduction can be improved by increasing the bioparticle loading or the initial biomass loading. Glass bioparticles have shown better performance as compared to Ca-alginate bioparticles in terms of batch Cr(VI) reduction achieved and the rate of reduction. Glass beads may be considered as better cell carrier particles for immobilization as compared to Ca-alginate beads. Around 90% reduction of 80 ppm Cr(VI) could be achieved after 24 h with initial biomass loading of 14.6 mg on glass beads. Artificial neural network-based models are developed for prediction of batch Cr(VI) bioreduction using the cells immobilized on glass and Ca-alginate beads.

COMPETITIVE INTERACTIONS BETWEEN THE OPPORTUNISTIC MACROALGAE CLADOPHORA VAGABUNDA (CHLOROPHYTA) AND GRACILARIA TIKVAHIAE (RHODOPHYTA) UNDER EUTROPHIC CONDITIONS1

ABSTRACT In a eutrophic embayment (Waquoit Bay, Massachusetts), Cladophora vagabunda (L.) van den Hoek occurs in thick (sometimes > 1 kg dry wt ‐m−2), nearly monospecific unattached mats in deeper regions (2 m), whereas Grac‐ilaria tikvahiae McLachlan is largely restricted to shallow (<1 m) areas. We explored these distribution patterns, investigating competitive interactions between these opportunistic species by varying the limiting resource, photon flux density (PFD), and species composition under conditions of N sufficiency in microcosms. Under lower biomass loadings, neither species showed a difference in growth rates in single‐ and mixed‐species stands. With a 25% increase in initial biomass loading, Gracilaria tikvahiae had significantly higher growth rates under saturating PFD and consistently showed greater performance when grown in single‐species rather than in mixed‐species stands. While growth rate was 2×greater for C. vagabunda in single‐species than in mixed‐species stands at saturating PFD, this pattern was reversed under limiting irradi‐ances. In mixed‐species stands at high PFD (comparable to shallow regions of the bay), the growth rate of G. tikvahiae was over 4×higher than that of C. vagabunda. Cladophora vagabunda grew at a faster rate than G. tikvahiae only in the low PFD, mixed‐species treatment. Results of this study suggest that the observed distributional patterns of these macroalgae are due in part to interspecific exploitative competition but that tolerance of low PFD by C. vagabunda has led to dominance of these species in distinctive regions of the embayment.

THE DETERMINATION OF ANAEROBIC BIODEGRADABILITY OF PHARMACEUTICAL WASTES BY METHANOGENIC ACTIVITY TESTS

Methanogenic activity tests were used for the determination of anaerobic biodegradability of some concentrated wastes from the pharmaceutical industry - waste biomass from threonine production, mycelium after penicillium extraction, and excess activated sludge from the treatment of other pharmaceutical wastewaters. The tests were performed in 120 ml vials for each of the wastes ru1d for a mixture of the wastes in a real ratio. The mixture was tested at a wide range of initial biomass loading (1.15-8.8 gCOD/gVSS). The anaerobic biodegradability of the threonine biomass, the mycelium and the activated sludge was determined as 81.3%, 94.3% ru1d 44.4% respectively, and the average biodegradability of the mixture as 85.8%. Retention times needed for an 80% degradation efficiency were evaluated and used as a proposal for the starting-up biomass loading rate of the continuous reactor operation. An optimum substrate concentration without an inhibition effect was estimated and a specific methane yield for each waste; and for the mixture determined.