Applied Mechanics and Materials Vol. 737

Abstract: In order to treat the beet sugar factory wastewater and produce hydrogen, a low pH, ethanol-type fermentation process had happened in a continuous stirred tank reactor (CSTR) with an effective volume of 9.6 L in this experiment. The results showed that after inoculation with activated sludge and operation at organic loading rate (OLR) of 9 kgCOD/m³·d, hydraulic retention time (HRT) of 8h, influent pH value of 6.5 and temperature of 35°C for 30 days, the CSTR achieved stable ethanol-type fermentation. During this period of stable operation, the reactor showed a stable COD removal efficiency of 19.2% and hydrogen production rate of 0.1L/gMLSS·d. Effluent pH ranged from 4.0 to 4.5. The total amount of ethanol and acetic acid was 1384 mg/L, accounted for 81% of the total liquid products, which can be attributed to ethanol-type fermentation. The experimental results showed that the CSTR system had good operation stability and microbial activity, which led to high substrate conversion rate and hydrogen production ability.

Abstract: The number of ehromosome and karyotype of Hibiscus syriacus L. was analyzed with the root tips squash method. The results showed that the H. syriacus is tetraploid, the ehromosome number of the somatic cell of H. syriacus is 2n=56, and the index of relative length (IRL)= 16L+12M2+8M1+20S. The karyotype formula is K(2n)=4x=56=32m+16sm+8st, and the asymmetric index of karyotype is 62.90%. The karyotype belongs to 2B.

Abstract: The brine discharge from the seawater desalination plant will affect the receiving water to some extent in physics, chemistry, biology, and so on, especially harmful to the benthos and marine lives in the adjacent water area. In this paper, the experiment was conducted to investigate the effects of different salinities on the growth, survival rates in clam from low-salinity under controllable conditions in laboratory. The results show that individuals grew best at salinity 30 to 35. When the salinity exceeded 40, the survival rate and ILS₅₀ of the individuals decreased significantly. Therefore, it is necessary to develop effective means of reducing the negative influence of brine discharged on the marine environment.

Abstract: Present study was aimed to identify and isolate the red pigment from Serratia marcesce zl3, and to investigate the factors affecting on the light stability of the purified red pigment. Silica gel and Sephadex LH-20 column chromatography were used for purification, identification was done by TLC, UV, FTIR and HPLC-MS techniques. The effect of pH and light intensity on the light stability of the purified red pigment prodigiosin was analyzed by TLC, UV and HPLC. The stability of identified prodigiosin pigment at pH 1, 3, 5 was superior to that at pH 7, 10, 14 according to the determination of OD₅₃₅. Significant level of degradation of the prodigiosin was observed for 24 h, using 10 klx continuous white light. The effect of pH to the stability of prodidgiosin was partly reversible, while the degradation of prodigiosin under 4, 10, 20 klx white light was irreversible.

Abstract: 16SrDNA PCR-DGGE was used to reveal the dynamics of bacterial colony and identify the predominant bacteria in liquid-smoked tilapia during storage at 25°C. Total bacteria DNA was directly extracted from the tilapia fillets. By analysis of the community changes directly obtained from the DGGE profiles, the predominant bacteria were found to be Pediococcus pentosaceus, Clostridium sp. and Lactococcus garvieae. Simultaneously, culture method was performed., 34 strains of 70 colonies were picked up from samples of day 4 storage period, then 6 strains were picked up at random and identified by extracting their 16SrDNA and sequencing, it’s proved that they were all Lactococcus. So Two ways of identifying the predominant bacteria were almost consistent.

Abstract: The cassava residue was selected as carbon source to study the effect of biofloc technique (BFT) on water quality control, growth performance and seedling emergence in a 40 L culture water of litopenaeus vannamei nursery culture system. The BFA groups included Graded level of C/N (15/1, 20/1 and 25/1) with three parallel samples, compared to the control groups. At the end of the feeding trial 15 days, 10.7%, 14.4% and 46.8% significantly decreased in NH₄⁺-N concentration of the graded level of C/N (p<0.05); 80.2%, 96.0% and 96.2% distinctly decreased in NO₂^--N concentration (p<0.05); 81.4%, 57.8%, 151% obviously increased on seedling emergence (p<0.05) and 52.2%, 80.8%, 18.2% obviously increased on body weight (p<0.05). The present study elucidates that in the nursery system adding cassava residue as carbon source the culture water quality was evidently improved and heterotrophic bacterium, phytoplankton and zooplankton was also effectively obviously promoted.

Abstract: Heavy metals will be released to the water column during the sediment resuspension, causing the secondary pollution to the water ecosystem. In this study, the sediment collected from Zhushan Bay was placed in three similar pneumatic annular flumes where the wind speeds supplied by blast blowers were 3.21m/s, 5.95m/s and 8.78m/s respectively. The physicochemical parameters of the water and concentrations of metals in the water, plants and sediment were measured during the relevant experiments. The result showed that the concentrations of metals in the overlying water increased while it decreased in the pore water with the hydrodynamic disturbance. The aquatic plant Vallisneria natans bioaccumulated metals in the sediment and water, and the plant roots showed a higher ability in assimilating metals than the leaves. Meanwhile a positive correlation was found between wind speed and release amount of metals in pore water. In addition, the relationship between the wind speed and the biota-sediment accumulation factor (BSAF) was different due to the different features of metals.

Abstract: It is important to control Cadmium (Cd) content in rice and ensure the grain security. The transfer characteristics of Cd in paddy soil-rice system between different soil types (red soil and purple soil) under field condition were researched to provide a theoretical basis for Cd environmental management in paddy. In this study, many rice plant samples and corresponding paddy soil samples were collected from fields around the industrial and mining area in central Hunan province in 2011 and 2012. The Cd concentration of samples was analyzed, and the degree of Cd contamination was evaluated. Moreover, the differences of enrichment factor and influencing factors in paddy soil-rice system between red soil and purple soil were discussed. The results revealed that paddy soils and brown rice in the survey area were serious contaminated by Cd. The Cd content and enrichment factor were arranged in the order of root> straw >chaff >brown rice. The Cd content and enrichment factor were in the order of red soil >purple soil. In addition, multivariate linear regression was analyzed and predictions models of Cd concentration of brown rice are based on different types of soil were worked out. It showed that total Cd of soil, organic matter and clay were the main factors that affecting the content of Cd in brown rice. In conclusion, the contamination characteristics, transfer disciplinarian and influencing factors of Cd in the soil-rice system are different between red soil and purple soil. So it needs to pay more attention to the characteristics of different soil parent material when making environmental management related to Cd contamination in soil-rice system.

Abstract: We collected 17 soil samples from tobacco fields in Bijie City, Guizhou Province, Luzhou City, Sichuan Province. A total of 247 bacterial strains were isolated and 19 pairs of antagonism against Phytophthora nicotianae by tablet dual culture. Then six antagonistic and compatibility better bacterial strains were selected.. Further by antibacterial, pot and field experiments, come to the strain combination B41B57 and L7L47 have best inhibitory effect. At last, identified B41 as Bacillus subtilis, L7, L47 is B.amyloliquefaciens, B57 is Pseudomonas.putida by morphological observation, physiological and biochemical characteristics and 16SrDNA sequence analysis.

Abstract: Xylanase has good application prospect in the paper and pulp industry, feed industry, health care and bioenergy industry,etc.The xylanase is one of the key enzyme in the utilization of biomass. Fermentation kinetics equation was constructed based on Logistic and Luedeking-Piret equation. The results showed that the dissolved oxygen was related to the stirring speed, raising to 45% naturally after the log growth phase (about 30h) on the base of the optimum medium process of xylanase production by Trichoderma reesei. Fed-batch fermentation strategy was designed based on fermentation kinetics equations. The xylanase activity was further enhanced to 2406.175U/mL, enzyme activity per unit protein mass was 6573U/mg.