Hydrothermal vents in Lake Tanganyika harbor spore-forming thermophiles with extremely rapid growth

A thermophilic anaerobic bacterium was isolated from a sublacustrine hydrothermal vent site in Lake Tanganyika (East Africa) with recorded fluid temperatures of 66-103 °C and pH values of 7.7-8.9. The bacterium (strain TR10) was rod-shaped, about 1 by 5 μm in size, and readily formed distal endospores. Based on the 16 S rDNA sequence the novel strain was homologous to Thermobrachium celere and Caloramator indicus, which are closely related. The novel strain was strictly anaerobic, fermentative and had a doubling time as short as 10 min during growth on complex substrates, such as yeast extract and peptone. The optimum temperature for growth was 60 °C, while minimum and maximum temperatures were 40 and 75 °C. The pH response was alkalitolerant with optimum pH at 7.4 and 8.5 depending on the growth medium. The distinct feature of rapid proliferation and endospore formation may allow the novel organism to exploit the temporarily fluctuating growth conditions in the hydrothermal vent environments of Lake Tanganyika.     

Conventional and thermophilic aerobic treatability of high strength oily pet food wastewater using membrane-coupled bioreactors

Although thermophilic treatment systems have recently gained considerable interest, limited information exists on the comparative performances of membrane-coupled bioreactors (MBR) at thermophilic and conventional conditions. In this study aerobic MBRs operating at room temperature (20 degrees C) and at lower thermophilic range (45 degrees C) were investigated for the treatment of dissolved air flotation (DAF) pretreated pet food wastewater. The particular wastewater is characterized by oil and grease (O & G) concentrations as high as 6 g/L, COD of 51 g/L, BOD of 16 g/L and volatile fatty acid (VFA) of 8.3 g/L. The performances of the two systems in terms of COD, BOD and O & G removal at varying hydraulic retention time (HRT) are compared. COD removal efficiencies in the thermophilic MBR varied from 75% to 98% and remained constant at 94% in the conventional MBR. The O & G removal efficiencies were 66-86% and 98% in the thermophilic and conventional MBR, respectively. Interestingly, high concentrations of VFA were recorded, equivalent to 50-73% of total COD, in the thermophilic MBR effluent. The observed yield in the thermophilic MBR was 40% of that observed in the conventional MBR.     

Strategies for changing temperature from mesophilic to thermophilic conditions in anaerobic CSTR reactors treating sewage sludge

Thermophilic anaerobic digestion presents an advantageous way for stabilization of sludge from wastewater treatment plants. Two different strategies for changing operational process temperature from mesophilic (37 degrees C) to thermophilic (55 degrees C) were tested using two continuous flow stirred tank reactors operated at constant organic loading rate of 1.38 g VS/l reactor/day and hydraulic retention time of 20 days. In reactor A, the temperature was increased step-wise: 37 degrees C-->42 degrees C-->47 degrees C-->51 degrees C-->55 degrees C. While in reactor B, the temperature was changed in one-step, from 37 degrees C to the desired temperature of 55 degrees C, The results showed that the overall adaptation of the process for the step-wise temperature increment took 70 days in total and a new change was applied when the process was stabilized as indicated by stable methane production and low volatile fatty acids concentrations. Although the one-step temperature increase caused a severe disturbance in all the process parameters, the system reached a new stable operation after only 30 days indicating that this strategy is the best in changing from mesophilic to thermophilic operation in anaerobic digestion plants.     

Thermal resistance of vegetative thermophilic spore forming bacilli in skim milk isolated from dairy environments

Thirteen thermophilic bacilli, major contaminants of powdered milk products, were characterized regarding their heat sensitivity. All strains belong to the two species Geobacillus stearothermophilus and Anoxybacillus flavithermus. Five of the tested strains were classified as heat sensitive, one strain showed a low amount of vegetative cells and was not heat-treated. With the seven heat resistant strains, a pasteurization step (73 °C, 20 s) at laboratory-scale was applied. Two strains, both from the species G. stearothermophilus, could survive the heat treatment without an inactivation effect. One of those G. stearothermophilus strains was pasteurized on pilot-scale high-temperatures-short-time (HTST) and the cells were able to survive the treatment as well. For one A. flavithermus strain, thermal inactivation data was determined and modelled with two approaches. The work emphasizes, that milk pasteurization for the production of a low-spore powder regarding the vegetative cells is not sufficient. The adaptation of the process temperature is necessary.     

Preservation of Acidithiobacillus caldus: A moderately thermophilic bacterium and the effect on subsequent bioleaching of chalcopyrite

Four bacterial preservation methods: passage culture, sterile sand tube preservation, freezing preservation and freeze-drying preservation, were used to store Acidithiobacillus caldus strain S2, a moderately thermophilic bacterium. Among the four methods, the second is shown to be the best for short term preservation (6 months), and the fourth is the best for long term preservation (15 months). Specifically, the results show that using the second method, 32% cell viability was obtained after 6 months, and the cell survival rate reaches 17% using the fourth method after 15 months. In the bioleaching experiments, A. caldus strain S2 preserved via the second and the fourth methods, along with Leptospirillum ferriphilum strain YSK, were applied to bioleach chalcopyrite. Under the two preservation methods for A. caldus strain S2, the results show that 3.72 g/L and 1.68 g/L copper are extracted in the first 20 days and the maximum biomass delays to the 15th day and to the 18th day, respectively. When the bioleaching time was extended to the 40th day, copper extraction increased significantly to 5.02 g/L and 4.88 g/L, respectively. However, A. caldus strain S2 under no preservation, along with L. ferriphilum strain YSK, extract only 0.54 g/L Cu from the 20th day to the 40th day and finally release 5.14 g/L Cu. Therefore, the preserved culture shows almost the same total copper extraction as the unpreserved one in 40 days. As a result, sterile sand tube preservation and freeze-drying preservation greatly prolong the lag phase of cell growth without much decrease in the bioleaching ability of A. caldus strain S2.     

Buffering and nutrient effects of white mud from ammonia–soda process on thermophilic hydrogen fermentation from food waste

Hydrogen production via anaerobic fermentation may suffer from instability or inhibition due to volatile fatty acids concentrations and inorganic elements deviations from optimality. A slight addition of white mud from ammonia–soda process (WMA) to the fermentation may show a feasible implement approach to use as buffer and inorganic nutrient. Batch tests were conducted to study the effect of the WMA addition on the hydrogen fermentation of food waste (FW) for the purpose of the maximum hydrogen yield (MHY) while achieving process stability and microbial germination through the endogenous alkalinity and inorganic elements of WMA. This was attributed to the existence of calcium, sodium, magnesium, potassium and alkali-rich materials, like calcium carbonate. 3 g of WMA addition to 200 g FW and fermentation time of 36 h resulted in obtaining the MHY of 145.4 mL H₂/g VS, with a corresponding lag-phase time of 3.0 h. Under these operating conditions, the fermentation process demonstrated one of the highest measured stability with final pH 5.3.     

Thermophilic composting of municipal solid waste

Process of composting has been developed for recycling of organic fraction of municipal solid waste (MSW). The bioreactor design was modified to reduce the composting process time. The main goal of this investigation was to find the optimal value of time period for composting of MSW in thermophilic bioreactor under aerobic condition. The temperature profiles correlated well with experimental data obtained during the maturation process. During this period biological degraders are introduced in to the reactor to accelerate the composting process. The compost materials were analyzed at various stages and the environmental parameters were considered. The final composting materials contained large organic content with in a short duration of 40 days. The quantity of volume reduction of raw MSW was 78%. The test result shows that the final compost material from the thermophilic reactor provides good humus to build up soil characteristics and some basic plant nutrients.     

Impact of oral administration of compost extract on gene expression in the rat gastrointestinal tract

Oral administration of an extract consisting of compost fermented with thermophiles to pigs reduces the incidence of stillbirth and promotes piglet growth. However, the mechanism by which the compost extract modulates the physiological conditions of the animals remains largely unknown. Here, we investigate the effects of compost extract on the physiological responses in the intestine of a mammalian rat model. The level of fecal immunoglobulin A (IgA), which provides protection against pathogens and is secreted from the small intestine, was significantly higher in rats treated with continuous administration of the compost extract than in untreated rats after 2 months, but not after 1 month. However, the fecal IgA level was not significantly different in rats that received the filtered compost extract compared with the untreated rats or the rats that received the compost extract. Gene expression analyses of the small intestine indicated that several immune-related genes were upregulated following compost exposure. Specifically, the expression levels of lymphocyte chemoattractant chemokine CXCL13 and Granzyme B, which is released within cytotoxic T lymphocytes and natural killer cells, increased in the small intestinal tract following compost exposure. Based on these observations, it was postulated that the increased level of fecal IgA following compost exposure was associated with the expression of CXCL13 and Granzyme B in the intestinal tract. Thus, thermophile-fermented compost could contain microbes or substances that activate the rat's gut mucosal immune response.