Enzyme treatment to reduce solids and improve settling of sewage sludge

The effect of microbial enzymes in reducing the disposable solid content of sludge was investigated. A mixture of industrial cellulase, protease, and lipase, in equal proportion by weight, reduced total suspended solids (TSS) by 30–50% and improved settling of solids. An increase in solid reduction was observed with increasing enzyme concentration. The effect of combinations of enzyme treatments indicated that two-enzyme combinations of protease and cellulase produced better solid reduction than individual enzymes and that lipase further augmented this effect. Among the individual enzymes, protease produced a more settleable sludge as compared to cellulase and lipase. Adjustment of the pH of the enzymatically treated sludge to the acidic range (pH 2–4) further improved solid reduction, and adjustment to the alkaline range (pH 10–12) improved settleability. Journal of Industrial Microbiology & Biotechnology (2001) 26, 383–386. Received 01 November 2000/ Accepted in revised form 29 April 2001     

Different genetic backgrounds influence the secretory expression of the LKA1-encoded Lipomyces kononenkoae α-amylase in industrial strains of Saccharomyces cerevisiae

A haploid laboratory strain and four industrial (baking, brewing, wine, ATCC) strains of Saccharomyces cerevisiae were transformed with the Lipomyces kononenkoae -amylase-encoding gene (LKA1). These transformants displayed significant differences in terms of the level of secretory expression of LKA1 under control of the PGK1 promoter and terminator, as well as their ability to produce and secrete the LKA1-encoded rawstarch-degrading -amylase and to ferment starch. These results demonstrate the importance of the selection of appropriate host strains for yeast development pursuant to starch conversion into commercially important commodities via consolidated bioprocessing.     

Caffeine-inducible enzyme activity in Pseudomonas putida ATCC 700097

Caffeine (1,3,7-trimethylxanthine), a ubiquitous component of human diet has been suggested as a chemical indicator of ecosystem impacts of sewage spills and treated effluent discharges because it is not sufficiently metabolized by wastewater microorganisms. This study identified enzymes responsible for caffeine metabolism in sewage bacteria. Pseudomonas putida biotype A (ATCC 700097) originally isolated as a rare caffeine-degrading organism in domestic wastewater exhibited diauxic growth on caffeine, concomitant with the expression of a P450-type cytochrome and peroxidase enzyme activities. Initial growth phase lasted 13.8 ± 1.4 h with a growth rate that was five times slower than the secondary growth phase that lasted 5.5 ± 1.2 h. Molecular and enzymatic characteristics of the cytochrome P450-type enzyme differ from the previously described cytochrome P450 (P450_cam) of P. putida (ATCC 17453) involved in camphor metabolism. The caffeine-inducible cytochrome P450-type enzyme exhibited a carbon monoxide difference spectrum peak at 450 nm, but does not allow growth on camphor. Caffeine induced production of haem-associated peroxidase activity was confirmed with 3,3, 5,5-tetramethylbenzidine–H₂O₂ reaction in polyacrylamide gels. Polymerase chain reaction (PCR) primers derived from the gene for cytochrome P450_cam (camC) of P. putida (ATCC 17453) did not yield an amplification product when DNA extracted from P. putida strain ATCC 700097 was used as template. The data demonstrate that caffeine is metabolized through a specific biphasic pathway driven by oxygen-demanding enzymes.     

H2 production with anaerobic sludge using activated-carbon supported packed-bed bioreactors

Packed-bed bioreactors containing activated carbon as support carrier were used to produce H₂ anaerobically from a sucrose-limiting medium while acclimated sewage sludge was used as the H₂ producer. The effects of bed porosity (_b) and substrate loading rate on H₂ fermentation were examined using packed beds with _b of 70–90% being operated at hydraulic retention times (HRT) of 0.5–4 h. Higher _b and lower HRT favored H₂ production. With 20 g COD l^–1 of sucrose in the feed, the optimal H₂ production rate (7.4 l h^–1 l^–1) was obtained when the bed with _b=90% was operated at HRT = 0.5 h. Flocculation of cells enhanced the retention of sludge for stable operations of the bioreactor at low HRTs. The gas products resulting from fermentative H₂ production consisted of 30–40% H₂ and 60–70% CO₂. Butyric acid was the primary soluble product, followed by propionic acid and valeric acid.     

Decolorization of textile indigo dye by ligninolytic fungi

The indigo dye is extensively used by textile industries and is considered a recalcitrant substance, which causes environmental concern. Chemical products used on textile processing, which affect the environment through effluents, can be voluminous, colored and varied. Vat textile dyes, like indigo, are often used and dye mainly cellulosic fibers of cotton. Decolorization of this dye in liquid medium was tested with ligninolytic basidiomycete fungi from Brazil. Decolorization started in a few hours and after 4 days the removal of dye by Phellinus gilvus culture was in 100%, by Pleurotus sajor-caju 94%, by Pycnoporus sanguineus 91% and by Phanerochaete chrysosporium 75%. No color decrease was observed in a sterile control. Thin layer chromatography of fungi culture extracts revealed only one unknown metabolite of Rf=0.60, as a result of dye degradation.     

Industrial media and fermentation processes for improved growth and protease production by Tetrahymena thermophila BIII

Tetrahymena thermophila was cultivated on industrial by-product media. The composition of the best medium (with milk proteins) was optimised by a central composite design for growth and protease secretion. The optimal combination [1.07% (w/v) of yeast extract and 0.99% (w/v) of skimmed milk] improved biomass production by 46%. In a fermentation strategy, the pH must be regulated to produce no cell damage, lengthening the stationary phase and resulting in a more abundant protease production. To increase cell concentration and protease secretion, a continuous culture with cell recycling by microfiltration was successfully tested on ciliated protozoa. Journal of Industrial Microbiology & Biotechnology (2000) 24, 285–290. Received 28 July 1999/ Accepted in revised form 20 January 2000     

Stress in seabirds: causes, consequences and diagnostic value

We describe a range of anthropogenic stressors thatimpact seabirds, review the effects of these stressorson individuals and populations and discuss the roleand value of seabirds as monitors of marine ecosystemhealth. Stressors described are restricted to thosewhich affect seabirds directly or indirectly throughthe marine environment; we have not dealt withterrestrially based stressors such as introducedmammalian predators or loss of habitat, which canpotentially affect seabirds whilst breeding. Wediscuss three broad categories of stress in seabirds.Marine pollutants (including biologicallynon-essential heavy metals, oil, organic pesticidesand polychlorinated biphenyls (PCBs), and plastics),industrial fisheries (further divided into the effectsof depletion of prey stocks and direct mortality), andclimate change. Additionally we highlight the role ofseabirds as monitors of marine ecosystem health,taking the example of long-term mercury contaminationas a case study. We conclude that seabirds are exposedto an increasing array of potential stressors, andthat the impact of a particular source of stress onseabirds varies markedly between species in relationto foraging and breeding ecology. The most seriousthreat to seabirds is direct mortality of adultsresulting from industrial and commercial fishingactivities. In some cases this is a significant threatto individual populations or even entire species.     

Decolourisation of synthetic textile dyes by Phlebia tremellosa

Phlebia tremellosa decolourised eight synthetic textile dyes (200 mg l(-1)) by greater than 96% within 14 days under stationary incubation conditions. High performance liquid chromatography analysis of culture supernatants indicated that Remazol Black B was degraded by the fungus, however, complete mineralisation did not occur as a colourless organic breakdown product accumulated. Laccase activity was detectable in culture supernatants after 5 days when the fungus was grown in the presence of an artificial textile effluent, with activity reaching a maximum of 15 U l(-1) on day 14.     

Survey and analysis of commercial cellulase preparations suitable for biomass conversion to ethanol

Commercial cellulase enzymes have been used in the food, detergent, and textile industries, and are potentially effective for processing biomass feedstocks. A survey was undertaken to identify major manufacturers/distributors of cellulases in the USA and to evaluate 13 representative commercial preparations for enzyme activity, protein concentration, and chemical composition. Samples were subjected to activity measurements using filter paper, carboxymethylcellulose, cellobiose, and p-nitrophenyl--d-glucopyranoside as substrates. To ascertain the microbial origin of the commercial preparations, Western blots utilizing monoclonal antibodies specific for Trichoderma reesei CBH I and Aspergillus niger -d-glucosidase were developed. Eleven of the cellulases tested were of T. reesei or T. viride origin and two were from A. niger.     

化工废水生态毒性原因鉴别的实例研究

以南京市某一化工厂排出的废水为对象,对其生态毒性原因作了鉴别研究．结果表明,废水对Ｄａｐｈｎｉａｍａｇｎａ具有急性毒性,Ｃ１８固相提取可去除废水毒性,存在的主要毒物为非极性有机化合物．废水经Ｃ１８固相提取,发现废水中的主要可疑毒物为苯并吡喃酮和苯酚,是导致废水毒性的关键污染物,对废水毒性的贡献率分别为４４．６％和３２．９％．