Biosynthesis and Characterization of Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) from Bacillus cereus S10

The biodegradable and biocompatible copolymer poly-(3-hydroxybutyrate-co-5 mol% 3-hydroxyvalerate), poly-(3HB-co-5 mol% 3HV), was synthesized by Bacillus cereus S10 and the highest yield was determined as 69.91 % at pH 7 and 30 °C after 48 h of incubation using a glucose as the sole carbon source. Poly-(3HB-co-5 mol% 3HV) was purified from bacterial biomass using chloroform. FTIR analysis showed absorption bands at 1,723, 1,274, 1,373, 1,453, 2,932 cm^?1 corresponding to C=O, C–O stretching, CH₃, –CH₂ and –CH groups, respectively. ¹H-NMR and ¹³C-NMR analysis confirmed that the copolymer was composed of 95 mol% of 3-hydroxybutrate and 5 mol% of 3-HV monomeric units. Poly-(3-HB-co-5 mol% 3HV) was used for nanoparticles preparation. The diameter of nanoparticles was 202 nm.     

Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in compost

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or copolymers with 10% [P(3HB-co-10%3HV)] and 20% [P(3HB-co-20%3HV)] 3-hydroxyvaleric acid was studied in small household compost heaps. Degradation was measured through loss of weight (surface erosion) and changes in molecular weight and mechanical strength. It was concluded, on the basis of weight loss and loss of mechanical properties, that P(3HB) and P(3HB-co-3HV) plastics were degraded in compost by the action of microorganisms. No decrease inM _w could be detected during the degradation process. The P(3HB-co-20%3HV) copolymer was degraded much faster than the homopolymer and P(3HB-co-10%3HV). One hundred nine microbial strains capable of degrading the polymersin vitro were isolated from the samples used in the biodegradation studies, as well as from two other composts, and identified. They consisted of 61 Gram-negative bacteria (e.g.,Acidovorax facilis), 10 Gram-positive bacteria (mainlyBacillus megaterium), 35Streptomyces strains, and 3 molds.     

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from various carbon sources by batch-fed cultures ofAlcaligenes eutrophus

Copolyesters of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) were produced at 30°C from various carbon sources byAlcaligenes eutrophus under batch-fed growth conditions. The production of P(3HB-co-3HV) from butyric and pentanoic acids was effective under nitrogenlimited conditions, and the conversion of carbon sources into copolyester was as high as 56 wt% at a C/N molar ratio of 40. In contrast, under excess-nitrogen conditions (C/N<10), cell growth was good, while P(3HB-co-3HV) production was partially inhibited. The production of P(3HB-co-3HV) from fructose and propionic acid was almost completely inhibited under excess-nitrogen conditions.     

Increased 3HV Concentration in the Bacterial Production of 3-Hydroxybutyrate (3HB) and 3-Hydroxyvalerate (3HV) Copolymer with Acid-Digested Rice Straw Waste

Bacterial synthesis of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) copolymer [P(3HB-co-3HV)] using the hydrolysate of rice straw waste as a carbon source was affected by the composition of the hydrolysate, which depends highly on the rice straw pretreatment condition. Acid digestion with 2 % sulfuric acid generated larger production of P(3HB-co-3HV) than 6 % sulfuric acid, but 3HV concentration in the copolymer produced with 2 % acid hydrolysate was only 8.8 % compared to 18.1 % with 6 % acid hydrolysate. To obtain a higher 3HV mole fraction for enhanced flexibility of the copolymer, an additional heating was conducted with the 2 % acid hydrolysate after removal of residual rice straw. As the additional heating time increased a higher concentration of levulinic acid was generated, and consequently, the mole fraction of 3HV in P(3HB-co-3HV) increased. Among the conditions tested (i.e., 20-, 40-, 60-min), 60-min additional heating following 2 % sulfuric acid digestion achieved the highest 3HV mole fraction of 22.9 %. However, a longer heating time decreased the P(3HB-co-3HV) productivity, probably due to the increased intermediates concentrations acting as inhibitors in the hydrolysates. Therefore, the use of additional heating needs to consider both the increase in the 3HV mole fraction and the decrease in the P(3HB-co-3HV) productivity.     

Degradation of Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Some Soil Aspergillus spp.

Systematic screening of 45 soil fungi for degradation polyhydroxyalkanoic acids (PHAs) has led to the selection of 6 potent Aspergillus isolates belonging to A. flavus, A. oryzae, A. parasiticus, and A. racemosus. Degradation of PHAs as determined by tube assay method revealed that these Aspergillus spp. were more efficient in degrading poly(3-hydroxybutyrate) [P(3HB)] compared to copolymer of 3-hydroxybutyric acid and 3-hydroxyvaleric acid (P3HB-co-16% 3HV). Moreover, the extent of degradation in mineral base medium was much better than those in complex organic medium. For all the Aspergillus spp. tested, maximum degradation was recorded at a temperature of 37°C with significant inhibition of growth. The optimum pH range for degradation was 6.5–7.0 with degradation being maximum at pH 6.8. The extent of polymer degradation increased with increase in substrate concentration, the optimum concentration for most of the cultures being 0.4% and 0.2% (w/v) for P(3HB) and P(3HB-co-16%3HV) respectively. Supplementation of the degradation medium with additional carbon sources exerted significant inhibitory effect on both P(3HB) and P(3HB-co-16%3HV) degradation.     

Municipal Wastes Treatment and Production of Polyhydroxyalkanoate by Modified Two-Stage Batch Reactor

The municipal wastes were utilized as substrate for polyhydroxyalkanoate (PHA) using two strains of Bacillus licheniformis (PHAs-007, wild type and M2-12, mutant). Municipal wastes were subjected to separate wastewater and biosolid. Municipal biosolid was digested by anaerobic bacteria thereafter only the supernatant with soluble organic compounds was subjected into the PHA-producing reactor containing municipal wastewater. The mutant strain M2-12 gave the highest value of biomass (42.0 ± 2.0 g/L) and PHA concentration (37.4 ± 1.0 g/L with 88.9 % of dry cell weight, DCW) and reduced 76.5 % of soluble chemical oxygen demand after 60 h of cultivation. The value of pH, biochemical oxygen demand and total solid of the reclaimed wastewater after PHA recovery was 7.1, 20 and 97 mg/L, respectively. Moreover, the polymers produced by both strains of B. licheniformis were characterized. The resultant polymer from B. licheniformis PHAs-007 and M2-12 cultivated in the PHA-producing reactor was identified as poly-3-hydroxybutyrate-co-3-hydroxyvalerate [P(3HB-co-3HV)] and poly-3-hydroxybutyrate-co-4-hydroxybutyrate [P(3HB-co-4HB)], respectively. The results suggesting that the production of PHA by municipal wastes is feasible thus the PHA production stage can be integrated in waste treatment to produce PHA and treated municipal wastes at the same time.     

Accumulation of Polyhydroxyalkanoates by Rhizobacteria Underneath Nickel-Hyperaccumulators from Serpentine Ecosystem

Nickel-resistant bacteria isolated from underneath Ni-hyperaccumulators growing on serpentine soils were screened for production of polyhydroxyalkanoates. These rhizobacteria accumulated poly-3-hydroxybutyric acid [P(3HB)] accounting 3.9–67.7% of cell dry weight during growth in gluconate and/or glucose. Cupriavidus pauculus KPS 201 utilized only gluconate and accumulated about 67.7% P(3HB) while, Bacillus firmus AND 408 utilized both carbon sources for polymer synthesis. The isolates being resistant to Ni also accumulated substantial amount of P(3HB) when grown in presence of the heavy metal and this was revealed by transmission electron microscopic studies. Although B. firmus AND 408 produced only P(3HB) at higher concentrations of gluconate, C. pauculus KPS 201 synthesized copolymer of 3-hydroxybutyric acid (3HB) and 3-hydroxyvaleric acid (3HV) [P(3HB-co-3HV)]. In presence of 0.8% gluconate and 4 mM Ni, KPS 201 cells produced PHA amounting 81% CDW, which contained 76 and 24 mol% 3HB and 3HV monomers, respectively.     

Degradation of poly(3-hydroxybutyrate), PHB,by bacteria and purification of a novel PHB depolymerase fromComamonas sp.

Bacteria capable of growing on poly(3-hydroxybutyrate), PHB, as the sole source of carbon and energy were isolated from various soils, lake water, activated sludge, and air. Although all bacteria utilized a wide variety of monomeric substrates for growth, most of the strains were restricted to degrade PHB and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate, P(3HB-co-3HV). Five strains were also able to decompose a homopolymer of 3-hydroxyvalerate, PHV. Poly(3-hydroxyoctanoate), PHO, was not degraded by any of the isolates. One strain, which was identified asComamonas sp., was selected, and the extracellular depolymerase of this strain was purified from the medium by ammonium sulfate precipitation and by chromatography on DEAE-Sephacel and Butyl-Sepharose 4B. The purified PHB depolymerase was not a glycoprotein. The relative molecular masses of the native enzyme and of the subunits were 45,000 or 44,000, respectively. The purified enzyme hydrolyzed PHB, P(3HB-co-3HV), and—at a very low rate—also PHV. Polyhydroxyalkanoates, PHA, with six or more carbon atoms per monomer or characteristic substrates for lipases were not hydrolyzed. In contrast to the PHB depolymerases ofPseudomonas lemoignei andAlcaligenes faecalis T₁, which are sensitive toward phenylmethylsulfonyl fluoride (PMSF) and which hydrolyze PHB mainly to the dimeric and trimeric esters of 3-hydroxybutyrate, the depolymerase ofComamonas sp. was insensitive toward PMSF and hydrolyzed PHB to monomeric 3-hydroxybutyrate indicating a different mechanism of PHB hydrolysis. Furthermore, the pH optimum of the reaction catalyzed by the depolymerase ofComamonas sp. was in the alkaline range at 9.4.     

Pseudomonas lemoignei has five poly(hydroxyalkanoic acid) (PHA) depolymerase genes: A comparative study of bacterial and eukaryotic PHA depolymerases

Four polyhydroxyalkanoate (PHA) depolymerases were purified from the culture fluid ofPseudomonas lemoignei: poly(3-hydroxybutyrate) (PHB), depolymerase A (M _r , 55,000), and PHB depolymerase B (M _r , 67,000) were specific for PHB and copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) as substrates. The third depolymerase additionally hydrolyzed poly(3-hydroxyvalerate) (PHV) at high rates (PHV depolymerase;M _r , 54,000). The N-terminal amino acid sequences of the three purified proteins, of a fourth partially purified depolymerase (PHB depolymerase C), and of the PHB depolymerases ofComamonas sp. were determined. Four PHA depolymerase genes ofP. lemoignei (phaZ1,phaZ2,phaZ3, andphaZ4) have been cloned inEscherichia coli, and the nucleotide sequence ofphaZ1 has been determined recently (D. Jendrossek, B. Müller, and H. G. Schlegel,Eur. J. Biochem. 218, 701–710, 1993). In this study the nucleotide sequences ofphaZ2 andphaZ3 were determined.PhaZ1,phaZ2, andphaZ4 were identified to encode PHB depolymerase C, PHB depolymerase B, and PHV depolymerase, respectively.PhaZ3 coded for a novel PHB depolymerase ofP. lemoignei, named PHB depolymerase D. None of the four genes harbored the PHB depolymerase A gene, which is predicted to be encoded by a fifth depolymerase gene ofP. lemoignei (phaZ5) and which has not been cloned yet. The deduced amino acid sequences ofphaZ1–phaZ3 revealed high homologies to each other (68–72%) and medium homologies to the PHB depolymerase gene ofAlcaligenes faecalis T₁ (25–34%). Typical leader peptide amino acid sequences, lipase consensus sequences (Gly-Xaa-Ser-Xaa-Gly), and unusually high proportions of threonine near the C terminus were found in PhaZ1, PhaZ2, and PhaZ3. Considering the biochemical data of the purified proteins and the amino acid sequences, PHA depolymerases ofP. lemoignei are most probably serine hydrolases containing a catalytical triad of Asp, His, and Ser similar to that of lipases. A comparison of biochemical and genetic data of various eubacterial and one eukaryotic PHA depolymerases is provided also.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Purification of Aspergillus fumigatus (Pdf1) Poly(β-hydroxybutyrate) (PHB) Depolymerase Using a New, Single-Step Substrate Affinity Chromatography Method: Characterization of the PHB Depolymerase Exhibiting Novel Self-Aggregation Behavior

The extracellular poly(-hydroxybutyrate) (PHB) depolymerase of Aspergillus fumigatus Pdf1 was purified by a new, simple, one-step affinity chromatography method using the substrate PHB. The purified enzyme was glycosylated, with the molecular mass of 40 KD, and exhibited a novel self-aggregation behavior by means of hydrophobic interaction that was resolved by Triton X-100 (TX-100) pretreatment of enzyme and also TX-100 incorporation in the native gel. The apparent K _m value of purified enzyme for PHB was 119 g/mL and 3-hydroxybutyrate was detected as the main endproduct of PHB hydrolysis. The depolymerase was insensitive to phenylmethyl sulfonyl fluoride (PMSF), sodium azide, ethylenediaminetetraacetic acid (EDTA), and para-chloromercuric benzoic acid (PCMB), but was inactivated by dithioerythritol (DTT) and showed specificity for short chain-length poly(-hydroxyalkanoates) (PHAs) such as PHB, poly(hydroxyvalerate) (PHV), and copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Medium-chain-length PHA failed to get hydrolyzed. The enzyme, however, exhibited strong cross reactivity with the Comamonas sp. PHB depolymerase antibodies, but not with PHV depolymerase antibodies of Pseudomonas lemoignei. Southern hybridization and dot blot analysis of A. fumigatus Pdf1 genomic DNA with alkaline phosphatase labeled probes of P. lemoignei PHB and PHV depolymerase genes revealed no homology, although the enzyme hydrolyzed both PHB and PHV.     

Absorption characteristics of potassium carbonate-based solutions with rate promoters and corrosion inhibitors

In this research, absorbents for CO₂ capture were prepared by blending 30 wt% potassium carbonate, 3 wt% of a rate promoter, and 1 wt% of a corrosion inhibitor. Pipecolic acid, sarcosine, and diethanolamine were chosen as rate promoter candidates. Based on a rate promoter screening test for CO₂ loading capacity and absorption rate, pipecolic acid and sarcosine were selected to be used as rate promoters. 1,2,3-benzotriazole and ammonium thiocyanate were chosen as corrosion inhibitors, and they were mixed with a 30 wt% potassium carbonate-based absorbent mixture containing one of the rate promoters. The absorption rates for four absorbent solutions (30 wt% potassium carbonate?+?3 wt% pipecolic acid?+?1 wt% 1,2,3-benzotriazole, 30 wt% potassium carbonate?+?3 wt% pipecolic acid?+?1 wt% ammonium thiocyanate, 30 wt% potassium carbonate?+?3 wt% sarcosine?+?1 wt% 1,2,3-benzotriazole, and 30 wt% potassium carbonate?+?3 wt% sarcosine?+?1 wt% ammonium thiocyanate) were measured, tabulated, and graphically displayed. These types of absorbents can be used for capturing CO₂ under high temperature and pressure conditions, such as those found in coal-fired power plants.     

Accumulation of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid-co-4-hydroxyvaleric acid) by mutants and recombinant strains ofAlcaligenes eutrophus

Alcaligenes eutrophus accumulated a terpolyester of 3-hydroxybutyric acid (3HB), 3-hydroxyvaleric acid (3HV), and 4-hydroxyvaleric acid (4HV) during cultivation with 4HV as carbon and energy source under nitrogen starvation. The polyester accumulated by wild-type strains under these conditions contained 4HV at a molar fraction of approximately 5 mol% only. A catabolic pathway of 4HV was postulated, which included the activation of 4HV to 4HV-CoA and a conversion of 4HV-CoA to 3HV-CoA. Tn5::mob-induced mutants were isolated fromA. eutrophus HF39, which were affected in 4HV and/or valeric acid catabolism. Among 83 mutants were 27 4HV-negative or 4HV-leaky mutants; two mutants were identified which accumulated a terpolyester with a molar fraction of 10.1 to 22.7 mol% 4HV. In addition, a further increase in the molar fraction of 4HV in poly(3HB-co-3HV-co-4HV) and a two- to fourfold increase in the PHA synthase activity were monitored in these mutants or others and also in HF39, if the cells were complemented with the hybrid plasmid pHP1014::PP1, which contained the PHA biosynthesis genes ofA. eutrophus H16. Application of mutagenesis plus recombinant DNA techniques resulted in the accumulation of a terpolyester with up to 30 mol% 4HV and with approximately equimolar fractions of 3HB, 3HV, and 4HV.     

Nucleophilic substitution of poly(vinyl chloride) with iminoacetic acid and n-dodecanethiol

The modification of poly(vinyl chloride) was carried out with iminodiacetic acid (IDA, C₄H₇NO₄) and iminodiacetic acid dimethylester (IDADM, C₆H₁₁NO₄), as well as with n-dodecanethiol (DT, C₁₂H₂₆S) in the presence of K₂CO₃. The reaction was carried out at different temperatures below 100 °C with dimethyl formamide (DMF) and cyclohexanone as solvents. IDA did not show any reactivity, probably due to the dipolar character of the molecule. IDADM caused the elimination of HCl, while only substitution ratios of about 3 % were observed. However, the modification of PVC with DT resulted in a substitution rate of 18 % without elimination. DT-PVC showed excellent thermal properties, comparable with those of the unmodified polymer.     

Archaeal Poly (3-hydroxybutyrate) Polymer Production from Glycerol: Optimization by Taguchi Methodology

In this study the possibility of poly (3-hydroxybutyrate) production from glycerol was investigated and optimized by Halorcula sp. IRU1, a novel archaea isolated from Urmia lake, Iran in batch experiments. Using Taguchi methodology, three important independent parameters (glycerol, yeast extract and KH₂PO₄) were evaluated for their individual and interactive effects on poly (3-hydroxybutyrate) production. It was shown that the glycerol concentration was the most significant factor affecting the yield of poly (3-hydroxybutyrate). The optimum factor levels were a glycerol concentration of 8% (v/v), yeast extract 0.8% (w/v) and KH₂PO₄ 0.002% (w/v). The predicted value obtained for poly (3-hydroxybutyrate) production under these conditions was about 81.87%. We can conclude that Haloarcula sp. IRU1 has a high potential for synthesis of poly (3-hydroxybutyrate) from glycerol.     

Bacterial Poly(Hydroxyalkanoate) Polymer Production from the Biodiesel Co-product Stream

A co-product stream from soy-based biodiesel production (CSBP) containing glycerol, fatty acid soaps, and residual fatty acid methyl esters (FAME) was utilized as a fermentation feedstock for the bacterial synthesis of poly(3-hydroxybutyrate) (PHB) and medium-chain-length poly(hydroxyalkanoate) (mcl-PHA) polymers. Pseudomonas oleovorans NRRL B-14682 and P. corrugata 388 grew and synthesized PHB and mcl-PHA, respectively, when cultivated in up to 5% (w/v) CSBP. In shake flask culture, P. oleovorans grew to 1.3 ± 0.1 g/L (PHA cellular productivity = 13–27% of the bacterial cell dry weight; CDW) regardless of the initial CSBP concentration, whereas P. corrugata reached maximum cell yields of 2.1 g/L at 1% CSBP, which tapered off to 1.7 g/L as the CSBP media concentration was increased to 5% (maximum PHA cellular productivity = 42% of the CDW at 3% CSBP). While P. oleovorans synthesized PHB from CSBP, P. corrugata produced mcl-PHA consisting primarily of 3-hydroxyoctanoic acid (C_8:0; 39 ± 2 mol%), 3-hydroxydecanoic acid (C_10:0; 26 ± 2 mol%) and 3-hydroxytetradecadienoic acid (C_14:2; 15 ± 1 mol%). The molar mass (M_n) of the PHB polymer decreased by 53% as the initial CSBP culture concentration was increased from 1% to 5% (w/v). In contrast, the M_n of the mcl-PHA polymer produced by P. corrugata remained constant over the range of CSBP concentrations used.     

A comparison study on high-temperature water–gas shift reaction over Fe/Al/Cu and Fe/Al/Ni catalysts using simulated waste-derived synthesis gas

A comparative study on Fe/Al, Fe/Al/Cu, and Fe/Al/Ni catalysts in high-temperature water–gas shift reaction (HT–WGS) using simulated waste-derived synthesis gas has been carried out. The metal oxide (Cu and Ni) and aluminum incorporated Fe catalysts were designed to get highly active HT–WGS catalysts. Despite the high CO concentration in the simulated waste-derived synthesis gas, Fe/Al/Cu catalyst exhibited the highest CO conversion (84 %) and 100 % selectivity to CO₂ at a very high gas hourly space velocity (GHSV) of 40,057 h^?1. The outstanding catalytic performance is mainly due to easier reducibility, the synergy effect of Cu and Al, and the stability of the magnetite.     

Recovery of Nd and Dy from rare earth magnetic waste sludge by hydrometallurgical process

This paper describes a hydrometallurgical process for recovering neodymium (Nd) and dysprosium (Dy) from a magnetic waste sludge generated from the Nd–Fe–B(–Dy) manufacturing process. Phase analysis by XRD study revealed Nd(OH)₃ and Fe₂O₃ as main mineral phases, and chemical analysis by ICP showed the contents of 35.1 wt% Nd, 29.5 wt% Fe, 1.1 wt% Dy and 0.5 wt% B. A solution of 1 M HNO₃ + 0.3 M H₂O₂ was used to dissolve up to 98 % Nd and 81 % Dy, while keeping Fe dissolution below 15 % within 10 min. Fe dissolved in solution was completely removed as Fe(OH)₃ at pH 3 followed by precipitation of Nd and Dy with oxalic acid (H₂C₂O₄) and recovered 91.5 % of Nd and 81.8 % of Dy from solution. The precipitate containing Nd and Dy was calcined at 800 °C to obtain Nd₂O₃ as final product with 68 % purity, and final recovery of 69.7 % Nd and 51 % of Dy was reported in this process.     

Processing and characterization of a new biodegradable composite made of a PHB/V matrix and regenerated cellulosic fibers

In this study, a biodegradable composite consisting of a degradable continuous cellulosic fiber and a degradable polymer matrix—poly(3-hydroxybutyrate)-co-poly(3-hydroxyvalerate (PHB/V with 19% HV)—was developed. The composite was processed by impregnating the cellulosic fibers on-line withPHB/V powder in a fluidization chamber. The impregnated roving was then filament wound on a plate and hot-pressed. The resulting unidirectional composite plates were mechanically tested and optically characterized by SEM. The fiber content was 9.9 ±0.9 vol% by volumetric determination. The fiber content predicted by the rule of mixture for unidirectional composites was 13.8 ±1.4 vol%. Optical characterization showed that the fiber distribution was homogeneous and a satisfactory wetting of the fibers by the matrix was achieved. Using a blower to remove excess matrix powder during processing increased the fiber content to 26.5 ±3.3 vol % (volumetric) or 30.0 ±0.4 vol% (rule of mixture). The tensile strength of the composite parallel to the fiber direction was 128 ±12 MPa (10 vol% fiber) up to 278 ±48 MPa (26.5 vol% fiber), compared to 20 MPa for the PHB/V matrix. The Young’s modulus was 5.8 ±0.5 GPa (10 vol% fiber) and reached 11.4 ±0.14 GPa (26.5 vol% fiber), versus 1 GPa for the matrix.     

Catalytic gasification of tars from a dumping site

The work deals with catalytic gasification, pyrolysis and non-catalytic gasification of tar from an industrial dumping site. All experiments were carried out in a vertical stainless steel gasification reactor at 800 °C. Crushed calcined dolomite was used as the gasification catalyst. Parameters such as addition of water and air, and the influence of the catalyst in regard to the composition of the process gas were investigated. The catalytic gasification experiment in the steady state produced process gas with the composition: 56 % of H₂, 9 % of CO, 11 % of CH₄ and 12 % of CO₂ (mol.%). Concentration of the C₂ fraction was lower than 1 mol.%. Volume flow of air was later changed from 120 to 230 ml min^?1 reducing the amount of hydrogen to 51 mol.% and that of methane to 10 mol.%. Process gas created in a non-catalytic gasification process contained 26–30 mol.% of methane, 13–15 mol.% of carbon monoxide and 15–17 mol.% of the C₂ fraction and lower amounts of hydrogen (20 mol.%) and carbon dioxide (2–3 mol.%). The highest apparent conversion of tar was reached in the catalytic gasification processes. A higher rate of catalyst deactivation can be observed when water or air is not added.     

Large-scale production of poly(3-hydroxyvaleric acid) by fermentation ofChromobacterium violaceum,processing, and characterization of the homopolyester

A fed-batch process was developed, which allowed biotechnological production of the homopolyester poly(3-hydroxyvaleric acid) [poly(3HV)], in a mineral salts medium containing valeric acid as carbon source and complex nutrients as supplements byChromobacterium violaceum at a 10- and 300-L fermentation scale. This process yielded up to 40 g dry cell matter per L fermentation broth, and the cells contained up to 70% (w/w) poly(3HV). Poly(3HV), which was extracted from the cells with chloroform and was precipitated from this solvent with ethanol, was processed to test bars by injection molding or by press processing and to fibers by melt spinning. The unprocessed and processed poly(3HV) material was characterized with respect to the molecular weight and with respect to thermal, rheological, and mechanical properties. It was shown that it is possible to process biodegradable poly(3HV) thermoplastically and to obtain a polymer suitable for applications with low strength requirements.