Microwave-assisted one-pot conversion of agro-industrial wastes into levulinic acid: An alternate approach.

Brewery liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry waste (SIW) were evaluated as alternative feedstocks for levulinic acid (LA) production via microwave-assisted acid-catalyzed thermal hydrolysis. LA production of 204, 160, 66, 49 and 12 g/kg was observed for BLW, BSG, APS, APUS, and SIW, respectively, at 140 °C, 40 g/L substrate concentration (SC), 60 min and 2 N HCl (acid concentration). Based on the screening studies, BLW and BSG were selected for optimization studies using response surface methodology. Maximum LA production of 409 and 341 g/kg for BLW and BSG, respectively were obtained at 160 °C, 4.5 M HCl, 85 g/L SC and 27.5 min. Results demonstrated the possibility of using brewery wastes as promising substrates for economical and higher yield production of LA, a renewable platform chemical and versatile precursor for fuels and chemicals.

Hydrolytic pre-treatment methods for enhanced biobutanol production from agro-industrial wastes.

Brewery industry liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry wastewater (SIW) have been considered as substrates to produce biobutanol. Efficiency of hydrolysis techniques tested to produce fermentable sugars depended on nature of agro-industrial wastes and process conditions. Acid-catalysed hydrolysis of BLW and BSG gave a total reducing sugar yield of 0.433 g/g and 0.468 g/g respectively. Reducing sugar yield from microwave assisted hydrothermal method was 0.404 g/g from APS and 0.631 g/g from APUS, and, 0.359 g/g from microwave assisted acid-catalysed SIW dry mass. Parameter optimization (time, pH and substrate concentration) for acid-catalysed BLW hydrolysate utilization using central composite model technique produced 307.9 g/kg glucose with generation of inhibitors (5-hydroxymethyl furfural (20 g/kg), furfural (1.6 g/kg), levulinic acid (9.3 g/kg) and total phenolic compound (0.567 g/kg)). 10.62 g/L of acetone-butanol-ethanol was produced by subsequent clostridial fermentation of the substrate.

A Unique Historical Case to Understand the Present Sustainable Development.

Every innovation seeks to become a profitable business, with this considered to be the engine for economic prosperity. When an innovation is revolutionary, its long-term consequences can be revolutionary too. The Haber-Bosh process for ammonia synthesis is arguably the twentieth century's most significant innovation, and its importance to global food production and its impact on the environment are not expected to diminish over the coming decades. The historical case of the ammonia synthesis process invented by Fritz Haber and the ensuing innovation provides an incomparable opportunity to illustrate the interactions across contemporary needs, prominent scientists, political concerns, moral dilemmas, ethics, governance and environmental implications at a time when the concept of sustainability was still in its infancy. Despite its high economic and environmental costs, no cleaner or more efficient sustainable alternative has so far been found, and so replacing this "old" innovation that still "feeds" a large part of the world's population does not appear to be on the cards in the near future.

Biomachining: metal etching via microorganisms.

The use of microorganisms to remove metal from a workpiece is known as biological machining or biomachining, and it has gained in both importance and scientific relevance over the past decade. Conversely to mechanical methods, the use of readily available microorganisms is low-energy consuming, and no thermal damage is caused during biomachining. The performance of this sustainable process is assessed by the material removal rate, and certain parameters have to be controlled for manufacturing the machined part with the desired surface finish. Although the variety of microorganisms is scarce, cell concentration or density plays an important role in the process. There is a need to control the temperature to maintain microorganism activity at its optimum, and a suitable shaking rate provides an efficient contact between the workpiece and the biological medium. The system's tolerance to the sharp changes in pH is quite limited, and in many cases, an acid medium has to be maintained for effective performance. This process is highly dependent on the type of metal being removed. Consequently, the operating parameters need to be determined on a case-by-case basis. The biomachining time is another variable with a direct impact on the removal rate. This biological technique can be used for machining simple and complex shapes, such as series of linear, circular, and square micropatterns on different metal surfaces. The optimal biomachining process should be fast enough to ensure high production, a smooth and homogenous surface finish and, in sum, a high-quality piece. As a result of the high global demand for micro-components, biomachining provides an effective and sustainable alternative. However, its industrial-scale implementation is still pending.

Role of Thiobacillus thioparus in the biodegradation of carbon disulfide in a biofilter packed with a recycled organic pelletized material.

This study reports the biodegradation of carbon disulfide (CS2) in air biofilters packed with a pelletized mixture of composted manure and sawdust. Experiments were carried out in two lab-scale (1.2 L) biofiltration units. Biofilter B was seeded with activated sludge enriched previously on CS2-degrading biomass under batch conditions, while biofilter A was left as a negative inoculation control. This inoculum was characterized by an acidic pH and sulfate accumulation, and contained Achromobacter xylosoxidans as the main putative CS2 biodegrading bacterium. Biofilter operation start-up was unsuccessfully attempted under xerophilic conditions and significant CS2 elimination was only achieved in biofilter A upon the implementation of an intermittent irrigation regime. Sustained removal efficiencies of 90-100 % at an inlet load of up to 12 g CS2 m(-3) h(-1) were reached. The CS2 removal in this biofilter was linked to the presence of the chemolithoautotrophic bacterium Thiobacillus thioparus, known among the relatively small number of species with a reported capacity of growing on CS2 as the sole energy source. DGGE molecular profiles confirmed that this microbe had become dominant in biofilter A while it was not detected in samples from biofilter B. Conventional biofilters packed with inexpensive organic materials are suited for the treatment of low-strength CS2 polluted gases (IL <12 g CS2 m(-3) h(-1)), provided that the development of the adequate microorganisms is favored, either upon enrichment or by inoculation. The importance of applying culture-independent techniques for microbial community analysis as a diagnostic tool in the biofiltration of recalcitrant compounds has been highlighted.

Reverse-flow strategy in biofilters treating CS2 emissions.

The bacteriostatic properties of carbon disulphide (CS2) hamper its biodegradation in conventional biofilters. The response of four biofilters operating in downflow mode and reverse-flow mode was compared in a laboratory-scale plant treating CS2 under sudden short-term changes in operating conditions. A process shutdown for 24 h, an inlet concentration increase and an interruption of the inlet air humidification for 48 h at an empty bed residence time (EBRT) of 240 s did not impact significantly on biodegradation performance, regardless of flow mode. Nevertheless, a reduction in the EBRT to 60 s resulted in a significant decrease in removal efficiency in all the biofilters. The CS2 degradation profile showed that the reverse-flow mode strategy rendered a more homogenous distribution of biomass along the bed height. The benefits of the reverse-flow mode were demonstrated even when the unidirectional flow mode was re-established.

Fungal/bacterial interactions during the biodegradation of TEX hydrocarbons (toluene, ethylbenzene and p-xylene) in gas biofilters operated under xerophilic conditions.

The treatment of air contaminated with toluene, ethylbenzene, and p-xylene was assayed in three laboratory-scale biofilters, each consisting of two modules connected in series, packed with a pelletized organic fertilizer and inoculated with a toluene-degrading liquid enrichment culture. Biofilters were operated in parallel for 185 days in which the volumetric organic loading rate was progressively increased. The operation regime was subjected to drying out, so that packing humidity generally remained below 40%. Significant process failure occurred with ethylbenzene and p-xylene, but the toluene biofilter comparatively sustained a significant elimination capacity. Microbial community characterization by quantitative PCR and denaturing gradient gel electrophoresis showed substantial fungal enrichment in the toluene biofilter. Ribotypes identical to the well-known toluene-degrading black yeast Exophiala oligosperma (Chaetotyriales) were found among the dominant species. The microbial community structure was similar in the biofilters loaded with toluene and ethylbenzene but with p-xylene was quite specific and encompassed other chaetothyrialean fungi. Several species of Actinomycetales were found in the packing while the inoculum was dominated by representatives of the Burkholderiales and Xanthomonadales. One single fungal ribotype homologous to Acremonium kiliense was detected in the inoculum. The implications of xerophilic biofilter operation on process biosafety and efficiency are discussed.