High density cell culture of a marine photosynthetic bacterium Rhodovulum sp. with self-flocculated cells

High density cell cultivation of a marine photosynthetic bacterium, Rhodovulum sp. PS88 with self-flocculated cells was established by using a single-tower fermenter. High density cell culture with continuous cultivation was yielded 43 g dry matter l–1 with acetate as a substrate consumed at 22.5 g/l day. © Rapid Science Ltd. 1998     

Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter

This study examined a stirred-tank fermenter (STF) containing low-viscosity foaming liquids with an agitation impeller and foam-breaking impeller mounted on the same shaft. Results showed that the performance of the foam-breaking impeller can be improved by changing a conventional six-blade turbine impeller into a rod impeller as the agitation impeller. The volumetric oxygen-transfer coefficient, k _L a, in the mechanical foam-control method (MFM) using a six-blade vaned disk as the foam-breaking impeller in the STF with the rod impeller was approximately five times greater than that of the chemical foam-control method (CFM) adding an anti-foaming agent in the STF with the six-blade turbine impeller. Application of the present method to the cultivation of Saccharomyces cerevisiae K-7 demonstrated that the cultivation time up to the maximum cell concentration was remarkably shorter than that achieved using a conventional CFM.     

Use of plant growth regulators in micropropagation of Kappaphycus alvarezii (Doty) in airlift bioreactors

The effects of plant growth regulators on callus induction rate and regeneration of K. alvarezii explants was evaluated. K. alvarezii calluses were induced in vitro with kinetin (K), 6-benzylaminopurine (B), 1-naphtalene acetic acid (N) and spermine (S). After 30 days, K. alvarezii explants produced filamentous calluses and isolated crystalline filaments growing from the medullar region and from cortical cells at the cut edge. The plant growth regulators 1-naphtalene acetic acid (1 mg L⁻¹) and 6-benzylaminopurine (1 mg L⁻¹) and the 1-naphtalene acetic acid + kinetin + spermine (1, 1, 0.018 mg L⁻¹ respectively) combination produced 85 to 129% more calluses, with significant differences versus the control (p<0.05). Spermine at 0.018 mg L⁻¹ produced calluses in the apical, intercalary and basal regions of explants. Spermine also reduced callus induction time to 7 days, which is faster than previously reported induction times with other plant growth regulators. An airlift bioreactor was designed and characterized to micropropagate K. alvarezii calluses. The bioreactor had mixing times ranging from 4.6–10.3 s at T ₉₀ and T ₉₅, which is shorter than those for the Fernbach (5.2–13.4 s) and balloon flasks (6.3–17.3 s). Mixing time standard deviations were smaller for the bioreactor (1.1–4.6) than for the Fernbach (9.3–13.6) and balloon flasks (5.5–15.8), suggesting an adequate flow regime within the bioreactor. The results are useful for improving callus induction in K. alvarezii and propagating microplantlets in an airlift bioreactor, and provide baseline data for macroalgal bioreactor culture.     

Coenzyme Q<Subscript>10</Subscript> production by <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis> in stirred tank and in airlift bioreactor

A higher Coenzyme Q₁₀ (CoQ₁₀) concentration of 25.04 mg/l was found in airlift bioreactor than the value of 18.11 mg/l obtained in stirred tank under the aerobic-dark cultivation of Rhodobacter sphaeroides. Aeration rate didn’t show obvious impact to CoQ₁₀ production in airlift bioreactor. The fed-batch operation in airlift bioreactor could increase the biomass concentration and led to the maximum CoQ₁₀ concentration of 33.91 mg/l measured, but a lower CoQ₁₀ cell content (3.5 mg CoQ₁₀/DCW) was observed in the fed-batch operation as compared to the batch operation. To enhance the CoQ₁₀ content, an aeration-change strategy was proposed in the fed-batch operation of airlift bioreactor. This strategy led to the maximum CoQ₁₀ concentration of 45.65 mg/l, a 35% increase as compared to the simple fed-batch operation. The results of this study suggested that a fed-batch operation in airlift bioreactor accompanying aeration-change could be suitable for CoQ₁₀ production.     

The relationship between forage cell wall content and voluntary food intake in mammalian herbivores

• 1 It is generally assumed that animals compensate for a declining diet quality with increasing food intake. Differences in the response to decreasing forage quality in herbivores have been postulated particularly between cattle (ruminants) and horses (hindgut fermenters). However, empirical tests for both assumptions in herbivorous mammals are rare.
• 2 We collected data on voluntary food intake in mammals on forage‐only diets and related this to dietary neutral detergent fibre (NDF) content, assuming a nonlinear correlation between these measurements. Generally, the paucity of corresponding data is striking.
• 3 Elephants and pandas showed very high food intakes that appeared unrelated to dietary fibre content. Only in small rodents, and possibly in rabbits, was an increase in food intake on forages of higher NDF content evident. In particular, other large herbivores, including horses, followed patterns of decreasing intake with increasing forage NDF, also observed in domestic cattle or sheep.
• 4 For large herbivores, empirical data therefore do not – so far – support the notion that intake is increased in response to declining diet quality. However, data are in accord with the assumption that most large herbivores have an anticipatory strategy of acquiring body reserves when high‐quality forage is available, and reducing food intake (and potentially metabolic losses) when only low‐quality forage is available.
• 5 Intake studies in which the influence of digestive strategy on food intake capacity is tested should be designed as long‐term studies that outlast an anticipatory strategy and force animals to ingest as much as possible.
• 6 We suggest that a colonic separation mechanism coupled with coprophagy, in order to minimize metabolic faecal losses, is necessary below a body size threshold where an anticipatory strategy (living off body reserves, migration) is not feasible. Future studies aimed at investigating fine‐scale differences, for example between equids and bovids, should focus on non‐domesticated species.

     

Production of antifungal saponins in an airlift bioreactor with a cell line transformed from Solanum chrysotrichum and its activity against strawberry phytopathogens

Abstract

Biotechnology through plant cell cultures in bioreactors is a tool that allows increasing the production of secondary metabolites of commercial interest. The hydrodynamic characterization, in addition to the transfer (OTR) and uptake (OUR) of oxygen through the dynamic method with different aeration rate, were used to see their influence on the production of biomass and saponins. The culture poisoning technique was used to determine the antifungal activity of the SC-2 and SC-3 saponins in vitro. Likewise, the shear or hydrodynamic stress of 273.6?mN/m² were calculated based on the Reynolds Number. The oxygen supply (OTR) was always greater than the demand (OUR) for all the aeration rate evaluated. Dry weight values of 8.6 gDW/L and a concentration of 2.7?mg/L and 187.3?mg/L of the saponins SC-2 and SC-3 respectively were obtained with an air flow of 0.1 vvm. In addition, it was possible to inhibit the growth of phytopathogenic fungi in vitro by up to 93%, while in vivo it was possible to reduce the infections of strawberry seeds inoculated with phytopathogens, obtaining up to 94% of germinated seeds. This information will facilitate the rational operation of the bioreactor culture system that produces secondary metabolites.     

Degradation of dimethyl-sulfoxide-containing wastewater using airlift bioreactor by polyvinyl-alcohol-immobilized cell beads

Airlift bioreactor containing polyvinyl-alcohol-immobilized cell beads was investigated for its capability of biodegradation of dimethyl sulfoxide (DMSO) in term of sludge characteristics including the strategy of acclimation with sucrose and the protection of microorganism from poisoning of DMSO by PVA cell beads. Media condition with sucrose at 50 mg L⁻¹ was beneficial to the biodegradation of DMSO in the fresh PVA entrapped-sludge, but became insignificant in the acclimated one as for tolerance of DMSO toxicity. The removal efficiency of DMSO had the highest rate at 1.42-kg DMSO per kilogram of suspended solid per day after series acclimation batches in the oxygen-enriched airlift bioreactor treated with the 1187.4 mg L⁻¹ of DMSO. Microbial consortium was required for the complete biodegradation of DMSO without any dimethyl sulfide produced. Pseudomonas sp. W1, excreting extracellular monooxygenase identified by indole, was isolated to be one of the most effective DMSO-degrading microorganism in our airlift bioreactor.     

A pilot study on lignocelluloses to ethanol and fish feed using NMMO pretreatment and cultivation with zygomycetes in an air-lift reactor

A complete process for the production of bioethanol and fungal biomass from spruce and birch was investigated. The process included milling, pretreatment with N-methylmorpholine-N-oxide (NMMO), washing of the pretreated wood, enzymatic hydrolysis, and cultivation of the zygomycetes fungi Mucor indicus. Investigated factors included wood chip size (0.5-16 mm), pretreatment time (1-5 h), and scale of the process from bench-scale to 2 m high air-lift reactor. Best hydrolysis yields were achieved from wood chips below 2 mm after 5 h of pretreatment. Ethanol yields (mg/g wood) of 195 and 128 for spruce, and 175 and 136 for birch were achieved from bench-scale and airlift, respectively. Fungal biomass yields (mg/g wood) of 103 and 70 for spruce, and 86 and 66 for birch from bench scale and airlift respectively were simultaneously achieved. NMMO pretreatment and cultivation with M. indicus appear to be a good alternative for ethanol production from birch and spruce.     

Influence of temperature rise on kinetic parameters during batch propagation of Kluyveromyces fragilis in cheese whey under ambient conditions

Three 5 l working volume fermenters were used to investigate the growth of the yeast Kluyveromyces fragilis in acid cheese whey under ambient temperature in order to assess the specific growth rate and yield, the lactose and oxygen uptake rates during the various phases of batch culture, the effect of increasing temperature on the various kinetic parameters, and the need for a cooling unit for single cell production batch systems. The initial dissolved oxygen in the medium was 5.5 mg l^–1 and the pH was maintained at 4.5. The observed lag phase, specific growth rate and maximum cell number were 4 h, 0.2 h^–1 and 8.4 × 10⁸ cells ml^–1, respectively. About 99% of the lactose in cheese whey was utilized within 20 h, 85% during the exponential growth phase. The specific lactose utilization rates by K. fragilis were 0.20 × 10^–12, 1.457 × 10^–12, 0.286 × 10^–12 and 0.00 g lactose cell^–1 h^–1, for the lag, exponential, stationary and death phases, respectively. The dissolved oxygen concentration in the medium decreased as the cell number increased. The lowest oxygen concentration of 1.2 mg l^–1 was observed during the stationary phase. The volumetric oxygen transfer coefficient was 0.41 h^–1 and the specific oxygen uptake rates were 0.32 × 10^–12, 2.14 × 10^–12, 0.51 × 10^–12 and 0.003 × 10^–12 mg O₂ cell^–1 h^–1, for the lag, exponential, stationary and death phases, respectively. The maximum temperature recorded for the medium was 33 °C, indicating that a cooling unit for batch production of single cell protein at ambient temperature is not needed for this type of bioreactor. The increase in medium temperature affected the cell growth and the lactose and oxygen uptake rates.