我国大豆生产波动动因分析——基于省际面板模型的实证研究

在我国大豆生产波动频繁的情况下,找出影响大豆单产、种植面积的影响因素是实现“提单产、稳面积”的首要举措。研究采用1999~2020年21个省份面板数据,在分析大豆单产、种植面积的变化趋势基础上,根据大豆单产增减趋势,把大豆产区划分成增产区、减产区和波动区,采用改进的面板数据模型分别对三个产区的大豆单产和种植面积的影响因素进行实证分析。结果表明,机械化收割、产研结合、农药投入、小型拖拉机的投入是影响不同区域大豆单产的显著因素;机械化耕作是提升所有区域种植面积的显著因素,玉米种植面积、化肥投入、农药投入、灌溉条件、科研资金与人员投入、产研结合、机械化收割是影响不同区域大豆种植面积显著因素。根据分析,提出了相应政策建议。

Continuous Lactic Acid Production from Longan Juice by Lactobacillus casei subsp, rhamnosus TISTR 108

This research focused using novel substrate, longan Lactobacillus casei subsp, rhamnosus TISTR 108. The optimum juice as carbon source for continuous lactic acid production by medium for lactic acid production was pure longan juice with 120 g/L sugar concentration and among the different nitrogen sources were added to the longan juice （yeast extract, tryptic soy, urea, （NH4）2SO4 and NaNO3）, yeast extract had the most efficiency. Yeast extract （10 g/L） without adding minerals to longan juice could produced the maximum lactic acid concentration of 38.91 ± 0.190 g/L in 60 h and the yield of 0.460± 0.122 g/g with the productivity of 0.649± 0.002 g/Lh in 2 liters flask. Batch fermentation was conducted in 2 liters fermentor and 41.38± 0.030 g/L lactic acid was produced in 48 h with the yield of 0.398 ± 0.215 g/g and the productivity was 0.862 ± 0.001 g/L h. The continuous fermentation using 2 liters fermentor as a high productivity for lactic acid （1.091 ± 0.001 g/L h） was achieved at dilution rate （D） of 0.0685 h-1.

Biosurfactant Production in Aerobic and Anaerobic Conditions by Different Species of the Genus Pseudomonas

In a time where surface active agents are capable of reducing the energy of the bonds between water molecules by interacting with them to reduce surface tension, it would be unwise not to be able to generate these in masses. Different Pseudomonas species were grown in MSP （minimal sulphate phosphate） media containing salts, glycerol and glucose. P. aeruginosa grown aerobically in the presence of glycerol as carbon source showed the highest emulsion percentage （81.48%）, most significant decrease in surface tension （20 mN/m） and rhamnose production of 2.86 mg/mL. However, in anaerobic conditions there was no emulsion, rhamnolipid production or decrease in surface tension. The rhamnolipids were molecularly characterized using ESI-MS （electrospray ionization-mass spectrometry）, P. aeruginosa CVCM 411 is able to produce mono-rhamnolipids and di-rhamnolipids, being rhamnolipid RhC10C12.1 the predominant monomer. The specific growth rate for isolates ofP. aeruginosa and P.fluorescens in MSP are 0.6732 ht and 0.2181 h^-1, respectively. In conclusion, the formation of rhamnolipids by P. aeruginosa is linked to its growth （depending on μ）, and its ability to generate about 35% of the μmax in the presence of glucose （carbon source） and glycerol （applied as pulses）.

Immobilization of Lactobacillus rhamnosus TISTR108 on Crude Pectin of Krung Kha Mao Leaves （Cissampe/os pareira L.） to Produce Lactic Acid in Longan Juice

L-（＋）-lactic acid production was studied by immobilized Lactobacillus rhamnosus T1STR108 on crude pectin from Krung Kha Mao Leaves. Central composite design was employed to determine the maximum lactic acid production of 42.88 g L-1 in predicted model with the factors at 4.11 g L1 of pectin, 6.05 mLLl inoculum and 1.09 mm of bead diameter. Statistical analyses demonstrated very high significance for the regression model, since the F-value computed 116.09 was much higher than the tabulated F-value 2.08 for the lactic acid production at 5% level for linear and quadratic polynomial regression models. The highest experimental lactic acid production was 43.57 g L^-1 at 96 h of fermentation, 1.58% higher than the predicted value.

Microwave induced mutagenesis of Lactobacillus casei subsp. rhamnosus for enhancing L-lactic acid production

Mutagenesis of Lactobacillus casei subsp, rhamnosus Xl-12 after low power microwave irradiation was investigated. Under a microwave power of 400 W and irradiation length of 3 min, a mutated strain W4-3-9 with high-yield L-lactic acid was obtained by screening. Compared with the starting strain X1-12, the L-lactic acid production of W4-3-9 was increased by 58.0% at a concentration of 115.8 g/L. The strain maintained the capability of producing a high L-lactic acid level after 10 generations. Cell surface morphology and DNA structures of parental and mutated strains were observed by atomic force microscopy （ AFM ）. Amplified fragment length polymorphism （AFLP） analysis suggested the difference in AFLP band pattern between the mutated and non-mutated strains. Sequencing and BLAST analysis revealed that the catalytic site of lactate dehydrogenase （DHL） was changed due to the microwave induced mutation.

Lactic Acid Production from Longan Juice （Euphora Iongana Lam.） by Crude Pectin of Immobilized Lactobacillus rhamnosus TISTRI08

L-（＋）-lactic acid production was studied by immobilized Lactobacillus rhamnosus TISTR108 on crude pectin from Krung Kha Mao （Cissampelospareira L.） leaves. Central composite design was employed to determine the maximum lactic acid production of 45.40 g/L in predicted model （Y = 43.98 - 2.43X1 ＋ 1.02X2 ＋ 2.96X3 - 8.72X1^2 - 3.99X2^2 - 1.74X3^2） with the factors at 5.9 of cultural medium pH, 37.6 ℃ of process temperature and 202 rpm of liquid agitation. Statistical analyses demonstrated very high significance for the regression model fitted the data adequately and explained the lactic acid production, since the F-value computed 54.89 was much higher than the tabulated F-value 2.08 for the lactic acid production at 5% level for linear and quadratic polynomial regression models. The highest experimental lactic acid production was 46.91 g/L at 72 h of fermentation.

Production and Recovery of Rhamnolipids Using Sugar Cane Molasses as Carbon Source

Biosurfactants were synthesized by Pseudomonas aeruginosa （P.A.）, using sugar cane molasses as carbon source. Assays were conducted in a shaker with agitation speed of 200 rpm, temperature of 38 ℃ and aeration ratio （Vm/Vf） of 0.4 and 0.6. A concentration of 3.0% was used for the carbon and energy source （molasses） and of 0.3% for the nitrogen source （NaNO3）. Samples were removed at regular times until 96 hours of cultivation. The reduction in surface tension was measured using the ring method; cell concentration was obtained by the dry mass and substrate consumption by the DNS method. The metabolite produced was extracted and quantified by the thioglycolic method. The results showed a maximum surface tension reduction of 46.57% after 60 h, 3.63 g/L of biomass after 8 h （μXmax =0.15 h^-1）, 79.60% of substrate consumption （μs= 0.67 h-1） and 4.47 g/L of rhamnolipid （μp=0.029 h^-1）.