餐厨垃圾厌氧干发酵产甲烷试验研究

为了探索餐厨垃圾高温干发酵的稳定性运行条件, 采用经三相分离后的餐厨垃圾为原料, 发酵罐污泥为接种污泥, 在高温干式条件下开展连续厌氧发酵产甲烷试验研究. 结果表明, 餐厨垃圾厌氧发酵产甲烷的最佳容积负荷为·(m3·d)-1, 容积产气率为·(m3·d)-1, 原料产气率为·(kg·d)-1, 甲烷体积分数为52.82%. 该厌氧干发酵产甲烷工艺可实现高温度、高含固率且高负荷条件下的稳定运行.     

Dynamics of cellulase production by glucose grown cultures of Trichoderma reesei Rut-C30 as a response to addition of cellulose

An economic process for the enzymatic hydrolysis of cellulose would allow utilization of cellulosic biomass for the production of easily fermentable low-cost sugars. New and more efficient fermentation processes are emerging to convert this biologic currency to a variety of commodity products with a special emphasis on fuel ethanol production. Since the cost of cellulase production currently accounts for a large fraction of the estimated total production costs of bioethanol, a significantly less expensive process for cellulase enzyme production is needed. It will most likely be desirable to obtain cellulase production on different carbon sources—including both polymeric carbohydrates and monosaccharides. The relation between enzyme production and growth profile of the microorganism is key for designing such processes. We conducted a careful characterization of growth and cellulase production by the soft-rot fungus Trichoderma reesei. Glucosegrown cultures of T. reesei Rut-C30 were subjected to pulse additions of Solka-floc (delignified pine pulp), and the response was monitored in terms of CO₂ evolution and increased enzyme activity. There was an immediate and unexpectedly strong CO₂ evolution at the point of Solka-floc addition. The time profiles of induction of cellulase activity, cellulose degradation, and CO₂ evolution are analyzed and discussed herein.     

In vitro stabilization of acv synthetase activity fromStreptomyces clavuligerus

ACV synthetase (ACVS) fromStreptomyces clavuligerus is very labile. The study and in vitro application of this important enzyme for cephamycin biosynthesis requires a relatively stable preparation. The stability of the crude enzyme was substantially increased by dithio-threitol and the cofactor, magnesium (Mg²⁺). The purified enzyme was also unstable and especially sensitive to moderate to high temperature. Addition of the substrate L-valine (L-val) along with the cofactors (ATP and MG²⁺) raised the thermal inactivation temperature, and increased the stability of the enzyme at low temperature. Amino acids capable of replacing L-val as ACVS substrate generally stabilized the enzyme. The ACVS level remained high during fermentation in a complex medium containing high concentrations of amino acids, in contrast to the situation in chemically-defined medium.     

Kinetics of asparaginase II fermentation in Saccharomyces cerevisiae ure2dal80 mutant

Although the quality of nitrogen source affects fermentation product formation, it has been managed empirically, to a large extent, in industrial scale. Laboratory-scale experiments successfully use the high-cost proline as a nonrepressive source. We evaluated urea as a substitute for proline in Saccharomyces cerevisiae ure2dal80 fermentations for asparaginase II production as a model system for nitrogen-regulated external enzymes. Maximum asparaginase II levels of 265 IU/L were observed in early stationary-phase cells grown on either proline or urea, whereas in ammonium cells, the maximum enzyme level was 157 IU/L. In all cases, enzyme stability was higher in buffered cultures with an initial pH of 6.5.     

Production of fumaric acid with immobilized biocatalysts

Immobilization ofRhizopus arrhizus mycelium improved fumaric acid production. The optimum conditions for fumaric acid production with immobilized cells were investigated using a statistical experimental design. Substrate concentration, carbon:nitrogen ratio, and residence time were chosen as independent variables. In the repeated batch shake flask fermentation, the fumaric acid yield from xylose was as much as 3.5 times higher with immobilized mycelium than with free mycelium. Polyurethane foam cubes, in this case, gave better results than nylon net cubes as a carrier.     

Evaluation of solid and submerged fermentations for the production of cyclodextrin glycosyltransferase by Paenibacillus campinasensis H69-3 and characterization of crude enzyme

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45°C, and is a Gramvariable bacterium. Different substrate sources such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed at 48–72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations. The optimum temperature was found to be 70–75°C, and the activity was stable at 55°C for 1 h. The enzyme displayed two optimum pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0.     

NMR identification of ethyl-linked anthocyanin-flavanol pigments formed in model wine ferments

The ethyl-linked pigments produced by the reaction between either catechin or epicatechin and malvidin 3-O-glucoside with added acetaldehyde have been isolated and characterised by NMR spectroscopy. These pigments are generated in high concentrations in model fermentations containing added malvidin 3-O-glucoside and (epi)catechin when inoculated with Saccharomyces cerevisiae yeast. This confirms that these pigments are produced during fermentation from metabolically produced acetaldehyde and provides evidence that the formation of these pigments may be a significant contributor to the purple colouration of young red wines.     

Continuous production of butanol with immobilized cells ofClostridium acetobutylicum

Spores ofClostridium acetobutylicum were immobilized in calcium alginate. An active gel preparation was obtained after outgrowth of the spores to vegetative cells within the gel matrix. A 100 mL column containing the immobilized cells was used for continuous production. At steady-state conditions the productivity of butanol was 67 g/L reactor volume/day.