2-Propanol degradation by Sulfolobus solfataricus

Sulfolobus solfataricus used 2-propanol and 2-propanone (acetone) when grown in static cultures at 78 °C with or without glucose at 10 g l^–1. The presence of 3.92 g 2-propanol l^–1 in both cases inhibited growth. However, acetone accumulation following 2-propanol depletion suggested that 2-propanol was co-metabolized via the acetone metabolic pathway. Glucose at 10 g l^–1 increased 2-propanol and acetone utilization from 0.93 g l^–1 to 1.77 g l^–1 and from 0.11 g l^–1 to 1.62 g l^–1, respectively. Without glucose, immobilized S. solfataricus cells increased the 2-propanol removal rate to 0.035 g l^–1 h^–1, compared to 0.0012 g l^–1 h^–1 by its suspended counterpart. The results suggest the establishment of an immobilized reactor configuration is preferential for the treatment of high temperature solvent waste streams by this acidothermophilic Crenarchaeon.     

Optimization of glycerol feeding for clavulanic acid production by Streptomyces clavuligerus with glycerol feeding

Glycerol at 10–20 g l^–1 increased clavulanic acid production by Streptomyces clavuligerus in shake-flask culture. The biosynthesis of clavulanic acid continued for longer by feeding glycerol and production increased to 250 mg l^–1 compared with 115 mg l^–1 without feeding. In fermenter batch culture, degradation of clavulanic acid began after 72 h. With glycerol feeding in fed-batch culture, clavulanic acid production was not only increased further to about 280 mg l^–1 but also remained stable up to 130 h.     

By-product formation by a novel glycerol-producing yeast,Candida glycerinogenes,with different O2 supplies

Candida glycerinogenes is an aerobe which does not depend on sulphite for production of glycerol. With a sufficient O₂ supply, up to 130 g glycerol l^–1 was produced with 2.6 g acetic acid l^–1 as by-product. However, with an insufficient O₂ supply – with higher volumes of medium or at higher corn steep liquid concentrations – the glycerol concentration was lower because the by-products, ethanol, pyruvate and lactic acid, were produced in greater amounts, up to 45 g l^–1, 4.3 g l^–1, 1.6 g l^–1, respectively, whereas, less acetic acid (0.6 g l^–1) was produced. In addition, ethanol decreased to 0.4 g l^–1 and the glycerol yield improved from 34 to 50% (w/w) by adding 50 g sulphite l^–1, nevertheless, acetic acid increased to 7.8 g l^–1.     

Improvement of cephalomanine production in Taxus chinensis cells by a combination of sucrose and methyl jasmonate

Cell suspension cultures of Taxus chinensis, supplemented with 25 g sucrose l^–1, produced 11 mg cephalomanine l^–1, 21 g biomass l^–1 and 19 nkat geranylgeranyl diphosphate (GGPP) synthase activity g protein^–1. Supplementation of the cultures with 100 M methyl jasmonate (MJA) produced 17 mg cephalomanine l^–1, 6 g biomass l^–1 and 78 nkat GGPP synthase activity g protein^–1. Addition of sucrose and MJA together produced 24 mg cephalomanine l^–1, 18 g biomass l^–1 and 55 nkat GGPP synthase activity g protein^–1.     

Kinetics of endosulfan degradation by Phanerochaete chrysosporium

The chlorinated pesticide, endosulfan, could be degraded by Phanerochaete chrysosporium under non-ligninolytic conditions, and this did not require direct contact with mycelium. The major metabolites formed were endosulfan sulfate and endosulfan diol. The rate of degradation depended on the initial concentration. With 2.5 mg endosulfan l^–1, degradation was at 0.23 mg l^–1 day^–1. The degradation could be described using a nonlinear rate expression that was similar to the Michaelis–Menten equation.     

Biodegradation of pyridine by freely suspended and immobilized Pimelobacter sp.

Freely suspended and Ca-alginate-immobilized cells of Pimelobacter sp. were used for degradation of pyridine. When the pyridine concentration was up to 2 g l^–1, freely suspended cells completely degraded pyridine regardless of the initial cell concentrations used. However, when the pyridine concentration increased to 4 g l^–1, the initial cell concentration in freely suspended cell culture should be higher than 1.5 g dry cell weight l^–1 for complete degradation of pyridine. In addition, a freely suspended cell culture with a high initial cell concentration resulted in a high volumetric pyridine-degradation rate, suggesting the potential use of immobilized cells for pyridine-degradation. When the immobilized cells were used for pyridine-degradation, neither specific pyridine-degradation rate nor tolerance against pyridine was improved. However, a high volumetric pyridine-degradation rate in the range 0.082–0.129 g l^–1 hr^–1 could be achieved by the immobilized cells because of the high cell concentration. Furthermore, when the immobilized cells were reused in degrading pyridine at a concentration of 2–4 g l^–1 they did not lose their pyridine-degrading activity for 2 weeks. Taken together, the data obtained here showed the feasibility of using immobilized cells for pyridine-degradation.     

Selective control of cyanobacteria by surfactin-containing culture broth of Bacillus subtilis C1

Of several types of chemical surfactants and biosurfactants, only the culture broth of Bacillus subtilis C1 containing surfactin at 10 mg l^–1 completely inhibited the growth of Microcystis aeruginosa, a bloom-forming cyanobacterium in highly eutrophic lakes. The broth with 10 mg surfactin l^–1 also removed 85% of the maximally grown M. aeruginosa (chlorophyll-a concentration, 1000 g l^–1) within 2 d, and the removal efficiency was enhanced by Ca²⁺ over 1 mM. The growth of Anabaena affinis, another bloom-forming cyanobacterium, was also inhibited about 70% with surfactin at 10 mg l^–1 broth. However, the effect of the broth was delayed over 3 d in the green algae, Chlorella vulgaris and Scenedesmus sp., and was negligible in a diatom, Navicula sp., indicating the potential for the selective control of cyanobacterial blooms.     

Production potential of eicosapentaenoic acid by the diatom Nitzschia laevis

To investigate the production potential of eicosapentaenoic acid (EPA) by the diatom Nitzschia laevis, the growth characteristics and fatty acid composition of the cells were studied under photoautotrophic, mixotrophic and heterotrophic conditions of growth. The specific growth rate and maximum biomass concentration were respectively 0.466 d^–1 and 2.27 g l^–1 for mixotrophic culture, 0.344 d^–1 and 2.04 g l^–1 for heterotrophic culture, and 0.167 d^–1 and 0.5 g l^–1 for photoautotrophic culture, respectively. As for EPA production, the yield and productivity were respectively 52.32 mg l^–1 and 10.46 mg l^–1 d for mixotrophic culture, 35.08 mg l^–1 and 6.37 mg l^–1 d for heterotrophic culture, and 6.78 mg l^–1 and 3.39 mg l^–1 d for photoautotrophic culture, respectively. Results suggest that mixotrophic culture is the most suitable growth mode for the production of EPA by the diatom Nitzschia laevis. The results are useful for the development of a cost-effective fermentation process for EPA production by Nitzschia laevis.     

Degradation kinetics of phenol by immobilized cells of Candida tropicalis in a fluidized bed reactor

Degradation kinetics of phenol by free and agar-entrapped cells of Candida tropicalis was studied in batch cultures. The initial phenol degradation rate achieved with free cells was higher than that obtained with immobilized cells, when phenol concentrations up to 1000 mg l^–1 were used. However, at higher phenol concentrations, the behaviour was quite different. The initial degradation rate of the immobilized yeast cells was about 10 times higher than that of the free cells, at a phenol concentration of 3500 mg l^–1. The semicontinuous and continuous degradation of phenol by immobilized yeast cells was also investigated in a multi-stage fluidized bed reactor. The highest phenol removal efficiencies and degradation rates as well as the lowest values of residual phenol and chemical oxygen demand were obtained in the semicontinuous culture when phenol concentrations up to 1560 mg l^–1 were used.     

Formation of phenylethanoid glycosides by Cistanche deserticola callus grown on solid media

The optimal growth of Cistanche deserticola callus and formation of phenylethanoid glycosides (PeG) was at 25°C with light irradiation intensity of 24 mol m^–2 s^–1 on solidified B5 media supplemented with 0.5 mg 6-benzylaminopurine l^–1, 10 mg gibberellin l^–1, 800 mg casein hydrolysate l^–1 and 20 g sucrose l^–1. After 30 d culture, the biomass reached 15.5 g dry wt callus l^–1 medium and its PEG content was 10.7% (w/w). The PeG content was 42%–127% higher than those in explants.     

Degradation of caffeine by immobilized cells of Pseudomonas putida strain C 3024

Summary A caffeine-resistant strain of Pseudomonas putida was isolated from soil and was grown with caffeine as the sole source of carbon, energy and nitrogen. Cells were immobilized in agar gel particles which were continuously supplied with a caffeine solution (0.52 g · l^–1, D=1.0 h^–1) in a homogeneously mixed aerated reaction vessel. In the presence of the ATPase inhibitor arsenate the caffeine was removed by the immobilized cells at an average rate of 0.25 mg caffeine · h^–1 · (mg cell carbon)^–1 during 6 days. Thereafter a rapid decline of activity was observed. From a similar system without arsenate supplied with a growth medium containing a limiting amount of caffeine (0.13 g · l^–1) the caffeine was almost completely oxidized by the immobilized cells. The concentration of the remaining caffeine was 1.4 mg · l^–1, which is much lower than the substrate constant for caffeine (9.7 mg · l^–1) observed with freshly harvested suspended resting cells.     

Reducing by-product formation in L-lactic acid fermentation by Rhizopus oryzae

During L-lactic acid fermentation by Rhizopus oryzae, increasing the phosphate level in the fermentation medium from 0.1 g l^–1 to 0.6 g l^–1 KH₂PO₄ reduced the maximal concentration of L-lactic acid and fumaric acid from 85 g l^–1 to 71 g l^–1 and from 1.36 g l^–1 to 0.18 g l^–1, respectively; and it decreased the fermentation time from 72 h to 52 h. Phosphate at 0.40 g l^–1 KH₂PO₄ was suitable for both minimizing fumaric acid accumulation and benefiting L-lactic acid production.     

Degradation of phenol by a defined mixed culture immobilized by adsorption on activated carbon and sintered glass

Summary A defined mixed culture of the yeast Cryptococcus elinovii H1 and the bacterium Pseudomonas putida P8 was immobilized by adsorption on activated carbon and sintered glass, respectively. Depending on its adsorption capacity for phenol the activated carbon system could completely degrade 17 g/l in batch culture, whereas the sintered glass system was able to degrade phenol up to 4 g/l. During semicontinuous degradation of phenol (1 g/l) both systems reached constant degradation times with the fourth batch that lasted 8 h when using the activated carbon system and 10 h in the sintered glass system. In the course of continuous degradation of phenol the activated carbon system reached a maximum degradation rate of 9.2 g l^–1 day^–1 compared to 6.4 g l^–1 day^–1degraded by the sintered glass system. 2-Hydroxymuconic acid semialdehyde could be identified and quantitatively determined as a metabolite of phenol degradation by P. putida P8. Increased membrane permeability under the influence of phenol was demonstrated by the examination of K⁺ efflux from P. putida P8. Offprint requests to: H.-J. Rehm     

Production of medium chain length polyhydroxyalkanoates by fed-batch culture of Pseudomonas oleovorans

Pseudomonas oleovorans was cultivated to produce medium chain length polyhydroxyalkanoates (MCL-PHAs) from octanoic acid and ammonium nitrate as carbon and nitrogen source, respectively, by a pH-stat fed-batch culture technique. The octanoate in the culture broth was maintained below 4 g l^–1 by feeding the mixture of octanoic acid and ammonium nitrate when the culture pH rose above 7.1. The final cell concentrations of 63, 55 and 9.5 g l^–1, PHA contents of 62, 75 and 67% of dry cell wt, and productivities of 1, 0.63 and 0.16 g l^–1 h^–1 were obtained when the C/N ratios in the feed were 10, 20 and 100 g octanoic acid g^–1 ammonium nitrate, respectively.     

A laboratory study of feeding and assimilation in Euchlanis dilatata lucksiana

Feeding of Euchlanis dilatata lucksiana, a brachionid rotifer isolated from the Loosdrecht Lakes (The Netherlands), was examined in the laboratory using ¹⁴C-labelled food. The gut-filling time at a food concentration of 9.6 µg C ml^–1 was about 15 minutes. Animals which were fed on 3 size fractions of the lake seston (< 7 µm, 7–15 µm, and 15–33 µm) showed a clear preference (Jacobs' selectivity index) for the largest size fraction. This fraction was composed predominantly of filamentous cyanobacteria. For animals weighing 0.37–0.49 µm C ind.^–1 the daily ration (daily food consumption per unit body weight × 100) ranged from 50 to 100% at food levels of 2 mg C l^–1 and below, but increased to 150–250% at food concentrations of 5 mg C l^–1 and above. The assimilation efficiency was 100% up to 5 mg C l^–1 of food, but decreased to about 80% at higher food levels.     

Bioconversion of compactin into pravastatin by Streptomyces sp.

Streptomyces sp. Y-110, isolated from soil, modified compactin to pravastatin, a therapeutic agent for hypercholesterolemia. In a batch culture, the highest production of pravastatin was 340 mg l^–1 from 750 mg compactin l^–1 in 24 h. By intermittent feeding of compactin into the culture medium, both the compactin concentration and its conversion increased to 2000 mg l^–1 and 1000 mg pravastatin l^–1, respectively, with the conversion rate of 10 mg l^–1 h^–1. Continuous feeding of compactin increased production of pravastatin to 15 mg l^–1 h^–1.     

Production of a fusion protein of sweet potato sporamin from recombinant E. coli XL1 Blue by fed-batch fermentations

Glucose-stat and pH-stat control strategies were employed in order to culture a recombinant E. coli XL1 Blue to produce a fusion protein of sweet potato sporamin (SPA) and glutathione S-transferase (GST) from the recombinant E. coli XL1 Blue. Cell densities up to 25 g l^–1 and 28.9 mg fusion protein (GST-SPA) g^–1 cell dry weight (CDW) was achieved from a fed-batch fermentation controlled by glucose-stat strategy. A pH-stat control fermentation using glycerol as a carbon source gave E. coli up to 27 g l^–1 and 31.5 mg GST-SPA g^–1 CDW. Additionally, a pH-stat control strategy using glucose as a carbon source gave E. coli up to 15 g l^–1 and about 22.7 mg g^–1 CDW of GST-SPA.     

Mixed inhibitions by methanol, furfural and acetic acid on xylitol production by Candida guilliermondii

Xylose production by Candida guilliermondii FTI 20037 was carried out in a synthetic medium in the presence of 0–100 g methanol l^–1, 0–0.7 g furfural l^–1 or 0–1.3 g acetic acid l^–1. Kinetic results show a mixed inhibition mechanism in all three cases. Maximum specific productivity and saturation constant for product formation were, in the absence of inhibition, 3.6 g_P g_X ^–1 h^–1 and 232 g_S l^–1, respectively, while the inhibition constants, K _i and K _i, were 17 and 50 g methanol l^–1, 0.62 and 7.0 g furfural l^–1, 0.69 and 3.5 g acetic acid l^–1, which suggests the following order of inhibition: furfural > acetic acid > methanol.     

Enhancement of paclitaxel production by abscisic acid in cell suspension cultures of Taxus chinensis

Addition of 5 mg abscisic acid l^–1 after 12 days' growth of Taxus chinensis suspension culture gave the greatest paclitaxel accumulation at 11 mg l^–1, which was almost 5 times that of the control culture. The highest paclitaxel production, 18 mg l^–1, was obtained using 5 mg abscisic acid l^–1 and 20 mg methyl jasmonate l^–1.     

Biotransformation of oleic acid into 10-hydroxy-8E-octadecenoic acid by Pseudomonas sp. 42A2

Pseudomonas sp. 42A2 when incubated for 36 h with oleic acid (20 g l^–1) in a stirred bioreactor, accumulated 10-hydroxy-8E-octadecenoic acid. Production in a 2 l bioreactor with 1.4 l of working volume, was increased from 0.65 g l^–1 to 7.4 g l^–1 with K _L a values ranging between 15 and 200 h^–1. A linear relationship was found between volumetric productivity and oxygen transfer rates and an exponential relation between the specific rate of product formation and specific growth rate.