Development of a two-phase combination fermenter for the conversion of cellulose to methane

Cellulose degradation to methane under continuous fermentation conditions was compared using fully mixed, fully mixed with solids return, sludge-blanket, and fixed-film fermenters. In fully mixed fermenters, a decrease in hydraulic retention time (HRT) of two weeks or less caused the wash out of anaerobes capable of converting volatile fatty acids to methane, while at increased feeding rates over 1 g/L day the rapid growth of cellulolytic anaerobes upset the balance between acid formation and its conversion to CH(4). Circulation of cellulose and difficulty in settling of cellulose with attached bacteria imposed problems in the use of other types of fermenters. On the basis of information obtained from this study, a fermenter which combined a fully mixed phase for cellulose degradation and a fixed-film phase with pre-immobilized bacteria for converting fatty acids to CH(4) in one vessel, was devised. Using this fermenter, a mixed culture converted cellulose to CH(4) at 4.8 g/L day at a HRT of six days as compared to 0.7 g/L day at a HRT of 28 days in the fully mixed fermenter.     

A comparison of some methods of estimating volumetric mass-transfer coefficients in an external-loop airlift fermenter

Volumetric mass-transfer coefficients were measured in an 11-L external-loop airlift fermenter with deionized water, a fermentation medium, and during a fermentation. Both a Mackareth oxygen electrode and a novel rapid-response probe were used. When the conventional step-change dynamic method was used for water, the long, nonlinear response time of the Mackareth electrode made correction of its readings difficult; this problem did not occur when the rapid-response probe was used. A comparison was made with a method of mass-transfer coefficient determination which does not involve any assumptions about the gas residence time distribution. However, this method requires that the liquid phase is well-mixed and this requirement was not met in the airlift fermenter. Comparison of the present results with other K(L) a determinations for airlift fermenters showed that K(L) a in water depends on the active gas holdup, the value of K(L) a/epsilon at 20 degrees C being ca. 0.37 s(-1). Although higher gas holdups were obtained with the fermentation medium than for water, the values of K(L) a/epsilon were lower, ca. 0.22 s(-1) at 20 degrees C.     

Low-pressure airlift fermenter for single cell protein production: II. Continuous culture of pichia yeast

Experiments using Pichia yeast grown on n-paraffins have been conducted in laboratory 10-L airlift fermenters and in a 640-L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low-pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low-pressure airlift fermenters become practical.     

Effects of minerals on feed degradation and protein synthesis by rumen micro-organisms in a dual effluent fermenter.

In dual outflow continuous fermenters on a 75:25 hay/barley diet, feed degradation and protein synthesis by mixed rumen microbes were tested in relation to the concentrations of HPO4(2-), HCO3- and Cl- and Na+/K+ ratio in artificial saliva, by applying a 16-run Franquart design, and by fitting second-order polynomial models. The HPO4(2-), HCO3-, Cl- concentrations and Na+/K+ ratio ranged from 0.1 to 4 g.L-1, from 0.5 to 7 g.L-1, from 0.1 to 0.5 g.L-1 and from 0.5 to 15 g.g-1, respectively. Buffer salts, particularly HPO4(2-), were the major factors while Cl- concentration had negligible effects on microbial metabolism. Maximal neutral detergent fibre, acid detergent fibre and organic matter degradabilities occurred at intermediate values of HPO4(2-) and HCO3- concentrations. The outflow of microbial protein and the efficiency of microbial protein synthesis, which varied from 26.2 to 37.1 g.N.kg-1 of organic matter truly degraded, reached minima at the centre of the experimental domain.     

Detection of microscopic leaks in fermenter cooling coils

Microscopic leaks in fermenter cooling coils were identified as the source of chronic fermentation contaminations. Methods used to identify the problem in production fermenters are described. Recommendations for upgrading quality control criteria for new installations are presented.     

Ability of DNA content and DGGE analysis to reflect the performance condition of an anaerobic biowaste fermenter

Molecular-microbiological techniques have delivered insight into microbial populations present in anaerobic fermenters, although much information still remains to be elucidated. In this study, the ability of denaturing gradient gel electrophoresis (DGGE) to throw light on microbial community composition was investigated and latter data were compared with the gas production of a 750,000l anaerobic biogas fermenter. During 1 year, samples were taken from two different sites of the reactor and additionally from the substrate material. After DNA extraction and PCR with archaeal and bacterial primers, PCR products were run on denaturing gradient gels to compare band patterns. Using gel-imaging software (GelComparII), two major clusters could be identified. Dominant bands were excised from the gels, reamplified and sequenced. Most sequences were closely related to Lactobacilli and yet uncultured microorganisms. DNA content of all samples was significantly correlated with the gas production measured online. We concluded that PCR and subsequent DGGE are useful to monitor community shifts in anaerobic fermenter sludge. However, as these changes are not readily detectable via DGGE-pattern analysis, alternative factors influencing the fermenter functioning should be found and investigated. So far DNA-content measurement seems to be a good parameter to quickly determine anaerobic fermenter condition.     

Maximum yield acetic acid fermenter.

Acetic acid fermenters in submerged culture are most currently used in vinegarmaking industry. However, they have the disadvantage of being open to the atmosphere with the subsequent evaporation losses of volatile compounds. This paper studies an acetic acid fermentation reactor equipped with a closed gas recycling system which prevents any loss of volatile compounds due to evaporation. Experiments have been conducted in two different operation regimes: fed-batch and continuous. Operation protocols are detailed for both cases, paying particular attention to optimum performance conditions, and comparison of yields and acetification rates.     

Shikimate pathway activity in shake and fermenter cultures of Cinchona succirubra

Cell suspension cultures of Cinchona succirubra were cultivated in shake cultures and for the first time in airlift fermenters. Under both conditions L-tryptophan exerts a stimulatory effect on alkaloid formation. In this context the regulatory pattern of some shikimate pathway enzymes was investigated in non-supplemented and tryptophan supplemented Cinchona cell cultures. A remarkable increase of tryptophan decarboxylase (TDC) activity was observed in Cinchona cells under the influence of tryptophan. Apparently, like in some other indole alkaloid producing cell cultures, a high TDC activity is a prerequisite for alkaloid formation. Growth pattern and some enzyme activities of C. succirubra fermenter cultures at controlled and non-regulated pH levels were followed. Optimum growth and alkaloid formation were recorded under non-regulated (normal) pH conditions.Abbreviations TDC tryptophan decarboxylase - try L-tyrosine - phe L-phenylalanine - DAHP 3-deoxy-D-arabino-heptulosonic acid-7-phosphate - trp L-tryptophan - E-4-P erythrose-4-phosphate - PEP phosphoenolpyruvate - MDH malate dehydrogenase - G-6-PDH glucose-6-phosphate dehydrogenase - 6-PG-DH 6-phosphogluconate dehydrogenase - Ch-mutase chorismate mutase - AS-synthase anthranilate synthase - n.d. not determined     

Towards the production of fungal biocontrol candidates using inert supports: a case of study of Trichoderma asperellum in a pilot fixed bed fermenter

The production of fungal biocontrol agents by solid-state fermentation (SSF) processes in inert supports demands deeper studies in SSF-modelling and SSF-optimisation to cope with scale-up issues. Here, we report the systematic application of fractional factorial and central composite designs to optimise the conidia productivity and maximum specific growth rate of the biological control candidate Trichoderma asperellum strain Th204 using two inert supports: polyurethane foam (PUF) and rice husk (RH), in a pilot 16 L fixed bed fermenter. By using response surface methodology, 2D contour graphs and Spearman’s correlation coefficients, axial temperature, conidia concentration, bed moisture and pressure drop gradients were modelled. C:N ratio and airflow rate were identified as significant factors. Optimal conditions using PUF a C:N ratio of 18.1 and airflow of 0.8?m³?h^?1 were found, with the highest productivity of 3.09?×?10⁷conidia g^?1 initial dry matter h¹. Polynomial models and response surfaces found in this study are advantageous to design strategies to scale-up the SSF process in fixed bed fermenters for fungal biological control candidates.     

Use of an aerodynamic foam quencher in the stab cultivation of mycelial fungi

A scheme for automatic impulse foam breaking during biosynthesis of cephalosporin C in 0.63 m3 pilot plant fermenters was developed and tested. It was shown that the use of an aerodynamic foam breaker did not limit the antibiotic biosynthesis by oxygen and promoted stabilization of the foam level in the apparatus without chemical antifoamers and increased air supply.     

Shifts in microbial populations in Rusitec fermenters as affected by the type of diet and impact of the method for estimating microbial growth (15N v. microbial DNA)

Rusitec fermenters are in vitro systems widely used to study ruminal fermentation, but little is known about the microbial populations establishing in them. This study was designed to assess the time evolution of microbial populations in fermenters fed medium- (MC; 50% alfalfa hay : concentrate) and high-concentrate diets (HC; 15 : 85 barley straw : concentrate). Samples from solid (SOL) and liquid (LIQ) content of fermenters were taken immediately before feeding on days 3, 8 and 14 of incubation for quantitative polymerase chain reaction and automated ribosomal intergenic spacer analysis analyses. In SOL, total bacterial DNA concentration and relative abundance of Ruminococcus flavefaciens remained unchanged over the incubation period, but protozoal DNA concentration and abundance of Fibrobacter succinogenes, Ruminococcus albus and fungi decreased and abundance of methanogenic archaea increased. In LIQ, total bacterial DNA concentration increased with time, whereas concentration of protozoal DNA and abundance of methanogens and fungi decreased. Diet×time interactions were observed for bacterial and protozoal DNA and relative abundance of F. succinogenes and R. albus in SOL, as well as for protozoal DNA in LIQ. Bacterial diversity in SOL increased with time, but no changes were observed in LIQ. The incubated diet influenced all microbial populations, with the exception of total bacteria and fungi abundance in LIQ. Bacterial diversity was higher in MC-fed than in HC-fed fermenters in SOL, but no differences were detected in LIQ. Values of pH, daily production of volatile fatty acids and CH₄ and isobutyrate proportions remained stable over the incubation period, but other fermentation parameters varied with time. The relationships among microbial populations and fermentation parameters were in well agreement with those previously reported in in vivo studies. Using ¹⁵N as a microbial marker or quantifying total microbial DNA for estimating microbial protein synthesis offered similar results for diets comparison, but both methods presented contrasting results for microbial growth in SOL and LIQ phases. The study showed that fermentation parameters remained fairly stable over the commonly used sampling period (days 8 to 14), but shifts in microbial populations were detected. Moreover, microbial populations differed markedly from those in the inocula, which indicates the difficulty of directly transposing results on microbial populations developed in Rusitec fermenters to in vivo conditions.     

Continuous ethanol fermentation using immobilized yeast cells

Growing cells of Saccharomyces cerevisiae immobilized in calcium alginate gel beads were employed in fluidizedbed reactors for continuous ethanol fermentation from cane molasses and other sugar sources. Some improvements were made in order to avoid microbial contamination and keep cell viability for stable long run operations. Notably, entrapment of sterol and unsaturated fatty acid into immobilized gel beads enhanced ethanol productivity more than 50 g ethanol/L gel h and prolonged life stability for more than one-half year. Cell concentration in the carrier was estimated over 250 g dry cell/L gel. A pilot plant with a total column volume of 4 kL was constructed and has been operated since 1982. As a result, it was confirmed that 8-10%(v/v)ethanol-containing broth was continuously produced from nonsterilized diluted cane molasses for over one-half year. The productivity of ethanol was calculated as 0.6 kL ethanol/kL reactor volume day with a 95% conversion yield versus the maximum theoretical yield for the case of 8.5% (v/v) ethanol broth.     

Reactor design for large scale suspension animal cell culture

The scale of operation of freely suspended animal cell culture has been increasing and in order to meet the demand for recombinant therapeutic products, this increase is likely to continue. The most common reactor types used are stirred tanks. Air lift fermenters are also used, albeit less commonly. No specific guidelines have been published for large scale (≥10 000 L) animal cell culture and reactor designs are often based on those used for microbial systems. However, due to the large difference in energy inputs used for microbial and animal cell systems such designs may be far from optimal. In this review the importance of achieving a balance between mixing, mass transfer and shear effects is emphasised. The implications that meeting this balance has on design of vessels and operation, particularly in terms of strategies to ensure adequate mixing to achieve homogeneity in pH and dissolved gas concentrations are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modelling of concentration profiles in tower fermenter. The influence of the axial dispersion coefficient

The production of CO₂ in tower fermenters which can cause back mixing, and thereby reducing the efficiency of such fermenters has been modelled with respect to fermentation. It is confirmed that the effect is significant. The effect of variations in the kinetic parameters, the maximum specific growth rate and the biomass yield coefficient was found to be insignificant. A good correlation between experimental and calculated data was obtained.     

Diversity and novelty of the gut microbial community of an herbivorous rodent (Neotoma bryanti)

Mammalian herbivores host diverse microbial communities to aid in fermentation and potentially detoxification of dietary compounds. However, the microbial ecology of herbivorous rodents, especially within the largest superfamily of mammals (Muroidea) has received little attention. We conducted a preliminary inventory of the intestinal microbial community of Bryant’s woodrat (Neotoma bryanti), an herbivorous Muroidea rodent. We collected woodrat feces, generated 16S rDNA clone libraries, and obtained sequences from 171 clones. Our results demonstrate that the woodrat gut hosts a large number of novel microorganisms, with 96% of the total microbial sequences representing novel species. These include several microbial genera that have previously been implicated in the metabolism of plant toxins. Interestingly, a comparison of the community structure of the woodrat gut with that of other mammals revealed that woodrats have a microbial community more similar to foregut rather than hindgut fermenters. Moreover, their microbial community was different to that of previously studied herbivorous rodents. Therefore, the woodrat gut may represent a useful resource for the identification of novel microbial genes involved in cellulolytic or detoxification processes.     

Microbial response to single‐cell protein production and brewery wastewater treatment

As global fisheries decline, microbial single‐cell protein (SCP) produced from brewery process water has been highlighted as a potential source of protein for sustainable animal feed. However, biotechnological investigation of SCP is difficult because of the natural variation and complexity of microbial ecology in wastewater bioreactors. In this study, we investigate microbial response across a full‐scale brewery wastewater treatment plant and a parallel pilot bioreactor modified to produce an SCP product. A pyrosequencing survey of the brewery treatment plant showed that each unit process selected for a unique microbial community. Notably, flow equalization basins were dominated by Prevotella, methanogenesis effluent had the highest levels of diversity, and clarifier wet‐well samples were sources of sequences for the candidate bacterial phyla of TM7 and BD1‐5. Next, the microbial response of a pilot bioreactor producing SCP was tracked over 1 year, showing that two different production trials produced two different communities originating from the same starting influent. However, SCP production resulted generally in enrichment of several clades of rhizospheric diazotrophs of Alphaproteobacteria and Betaproteobacteria in the bioreactor and even more so in the final product. These diazotrophs are potentially useful as the basis of a SCP product for commercial feed production.     

The continuous recovery of uranium from biologically leached solutions using immobilized biomass

The potential of uranium recovery from the dilute uranium ore bioleach solutions of the Elliot Lake district of Canada was examined using immobilized microbial biomass. Batch and continuous laboratory scale pilot plant experiments were carried out. The results have shown that the immobilized microbial biomass can successfully recover all of the uranium from dilute (less than 300 mg U/L) solutions. The uranium can subsequently be eluted producing a high uranium concentration eluate perhaps exceeding 5000 mg U/L. The biomass maintained its biosorption capacity of about 50 mg U/g over 12 examined successive adsorption-elution cycles with no apparent indication of failure.     

Characterization of plant polysaccharide- and mucin-fermenting anaerobic bacteria from human feces

Organisms able to grow on arabinogalactan, pectin, xylan, wheat bran, guar, apple cell walls, and mucin were isolated by enrichment from human feces. The number of polysaccharide fermenters and the properties of the predominant bacteria varied between subjects. The ability to use one polysaccharide was not related to the ability to use others. Some organisms (e.g., Bacteroides spp.) isolated on other substrates also utilized mucin, but were not isolated in the mucin enrichment. The mucin fermenters isolated by enrichment had a very restricted ability to utilize complex polysaccharides and their constituent monosaccharides, suggesting that the presence of plant polysaccharides in the human colon is unlikely to prevent the use of colonic mucin as an energy source by bacteria. Characterization with a range of biochemical tests showed that many of the isolates, but especially the mucin fermenters, did not resemble organisms described previously.     

Characterization of plant polysaccharide- and mucin-fermenting anaerobic bacteria from human feces.

Organisms able to grow on arabinogalactan, pectin, xylan, wheat bran, guar, apple cell walls, and mucin were isolated by enrichment from human feces. The number of polysaccharide fermenters and the properties of the predominant bacteria varied between subjects. The ability to use one polysaccharide was not related to the ability to use others. Some organisms (e.g., Bacteroides spp.) isolated on other substrates also utilized mucin, but were not isolated in the mucin enrichment. The mucin fermenters isolated by enrichment had a very restricted ability to utilize complex polysaccharides and their constituent monosaccharides, suggesting that the presence of plant polysaccharides in the human colon is unlikely to prevent the use of colonic mucin as an energy source by bacteria. Characterization with a range of biochemical tests showed that many of the isolates, but especially the mucin fermenters, did not resemble organisms described previously.     

哺乳动物的消化策略（英文）

理解动物的营养生态位是充分理解其整个生态学的基础,对于害兽控制和物种保护也很重要,食肉动物的小肠很发达,这可能与对食物的高消化能力有关;杂食性动物有更复杂的胃肠器官,其后端有可进行发酵的盲肠,消化物的平均滞留时间（mean retention times,MRTs)更长;最长的平均滞留时间见于食草动物,其消化道内高密度的微生物种群对不同滞留区内的消化物进行发酵,但是,并不是所有的食草动物都能够最大程度地消化植物纤维,只有反刍动物、骆驼和个体较大的后肠发酵动物（hindgut fermenter)能够具有这种能力,对比而言,许多其它的食草动物,如前肠发酵的有袋类和小型的后肠发酵动物如兔子、田鼠和负鼠等,它们具备可以使植物纤维消化效率最大的消化系统,可以在食物中的纤维素含量非常高的情况下仍能处理大量的食物。这些不同的消化策略使哺乳动物具有广幅的营养生态位。