Quantitative study of the reformation of excess sludge by intense aeration under nutrient-poor conditions

Abstrac  In the course of anaerobic storage of excess sludge, odors due to chemicals such as hydrogen sulfide are produced. These odors cause many problems. Many methods have been developed to eliminate odors, but all current methods are not only costly, but also largely ineffective. In this paper, we investigate the process of transformation of sludge microorganism cultures through intense aeration under nutrient-poor conditions, in terms of the selective adjustment and control of microorganism culture. The aerated sludge is subsequently returned to the adjusting pool, where the microorganisms inhibit odors, thus the excess sludge itself will act as an odor inhibitor. The process can be verified in terms of viability, in that the degradation capacity of the sludge was maintained after the intensely-aerated sludge was returned to the treatment system.     

Direct and indirect impacts of predation by fish on the zooplankton community: an experimental analysis using tanks

The impact of Pseudorasbora parva, a common zooplanktivorous fish species in Japan, on a zooplankton community was analyzed in experimental tanks, half of which were stocked with the fish. Different zooplankton species showed different responses to the introduction of the fish. In the presence of the fish, the populations of the large cladoceran Ceriodaphnia and the predatory copepod Mesocyclops were reduced, but the population of the herbivorous copepod Eodiaptomus and the small cladocerans Bosmina fatalis and Bosminopsis deitersi increased relative to the controls. The increase of Mesocyclops seen in the control tanks might have suppressed the populations of the small cladocerans, which are vulnerable to invertebrate predation. The results suggest that the population densities of the large prey items preferred by the fish, Ceriodaphnia and Mesocyclops, were controlled directly by fish predation, but the population densities of the smaller and less preferred zooplankton were controlled indirectly through the food-web cascade.     

Co-immobilized aerobic/anaerobic mixed cultures in stirred tank and gaslift loop reactors

Co-immobilized Aspergillus awamori and Zymomonas mobilis cultures were investigated in a stirred tank reactor on synthetic medium with starch as substrate at various dissolved oxygen concentrations. In a gaslift loop reactor, freely suspended and immobilized A. awamori were cultivated on synthetic medium and soluble potato starch. In the same reactor, the growth and ethanol production of freely suspended and immobilized Z. mobilis cultures were studied on synthetic medium and glucose. Co-immobilized A. awamori and Z. mobilis were cultivated in batch and continuous operations in the gaslift loop reactor on synthetic medium with starch substrate at different dissolved oxygen concentrations. The interrelations between the different process variables are discussed.     

Stimulation of bioluminescence in Noctiluca sp. using controlled temperature changes

Bioluminescence induced by multifarious stimuli has long been observed and is remains under investigation because of its great complexity. In particular, the exact mechanism underlying bioluminescence is not yet fully understood. This work presents a new experimental method for studying Noctiluca sp. bioluminescence under temperature change stimulation. It is a study of Noctiluca sp. bioluminescence using controlled temperature changes in a tank. A characteristic of this experiment is the large volume of water used (1 m³ in a tank of 2 × 1 × 1 m). Temperature changes were controlled by two methods. In the first, a flask filled with hot water was introduced into the tank and in the second, a water heater was used in the tank. Temperature changes were recorded using sensors. Noctiluca sp. bioluminescence was recorded using a Canon 5D Mark II and this allowed the characteristics of Noctiluca sp. bioluminescence under temperature change stimulation to be monitored. Copyright © 2012 John Wiley & Sons, Ltd.     

Biotransformation of pentacyclic terpene isolated from Alstonia scholaris (R.BR.)

Abstract

Betulin (1) a pentacyclic triterpene was isolated from medicinal plant Alstonia scholaris (R.BR.) and its structural modification by five filamentous fungi was investigated using flask shake and stirred bioreactor methods. Screening-scale and preparative-scale biotransformation with a standard two-stage protocol yielded betulinic acid (2). Out of five fungal strains (Microsporum canis, Trichophyton tonsurans, Aspergillus niger, A. niger NIAB-280 and Penicillium spp.) only two strains, M. canis and T. tonsurans, showed significant yield of (2). Samples withdrawn from fermentation medium were extracted with ethyl acetate and purified using column chromatography. Compound 2 was extracted from fermentation medium after 5–10 days. Flasks and the bioreactor were stirred at 250 rpm and 28°C. The yield of (2) gradually increased with incubation time. A stirred bioreactor was found to be convenient and simple for compound 1 oxidation. A validated analytical HPLC method was employed to confirm the biotransformation of compound 1 to 2.     

Non‐invasive online detection of microbial lysine formation in stirred tank bioreactors by using calorespirometry

Non‐invasive methods for online monitoring of biotechnological processes without compromising the integrity of the reactor system are very important to generate continuous data. Even though calorimetry has been used in conventional biochemical analysis for decades, it has not yet been specifically applied for online detection of product formation at technical scale. Thus, this article demonstrates a calorespirometric method for online detection of microbial lysine formation in stirred tank bioreactors. The respective heat generation of two bacterial strains, Corynebacterium glutamicum ATCC 13032 (wild‐type) and C. glutamicum DM1730 (lysine producer), was compared with the O₂‐consumption in order to determine whether lysine was formed. As validation of the proposed calorespirometric method, the online results agreed well with the offline measured data. This study has proven that calorespirometry is a viable non‐invasive technique to detect product formation at any time point. Biotechnol. Bioeng. 2013; 110: 1386–1395. © 2012 Wiley Periodicals, Inc.     

Comparative study for the effects of variable nutrient conditions on the biodegradation of microcystin-LR and concurrent dynamics in microcystin-degrading gene abundance

Microcystin-LR (MCLR) degradation capability of biofilm was investigated with and without additional nutrients (nitrate, ammonium, peptone and glucose) at concentrations of 100 and 1000 mg L(-1). The MCLR-degradation was stimulated with nitrate and inhibited with other nutrients, except for that glucose of low concentration had no obvious effect. Both stimulatory and inhibitory effects enhanced with increasing concentration of corresponding nutrient. Quantitative polymerase chain reaction (qPCR) indicated that enhanced inhibition in biodegradation correlated to increased inhibition in functional gene (mlrA) abundance, as nutrient concentration increased. Stimulated biodegradation under low nitrate concentration may result from more rapid increase in mlrA gene abundance. These suggested that MCLR-degradation largely depended upon responsible bacterial population, which was affected by population of other bacteria in biofilm according to 16S rDNA-targeting qPCR. However, inhibited mlrA gene abundance implied that the stimulated biodegradation under high nitrate concentration might be involved in the mechanisms not related to MCLRDB population.     

Treatment of waste gas from the breather vent of a vertical fixed roof p-xylene storage tank by a trickle-bed air biofilter

This study applied a pilot-scale trickle-bed air biofilter (TBAB) system for treating waste gas emitted from the breather vent of a vertical fixed roof storage tank containing p-xylene (p-X) liquid. The volatile organic compound (VOC) concentration of the waste gas was related to ambient temperature as well as solar radiation, peaking at above 6300 ppmv of p-X and 25000 ppmv of total hydrocarbons during the hours of 8 AM to 3 PM. When the activated carbon adsorber was employed as a VOC buffer, the peak waste gas VOC concentration was significantly reduced resulting in a stably and efficiently performing TBAB system. The pressure drop appeared to be low, reflecting that the TBAB system could be employed in the prolonged operation with a low running penalty. These advantages suggest that the TBAB system is a cost-effective treatment technology for VOC emission from a fixed roof storage tank.