Optimization of Fermentation Medium for Epothilones Production with Sequential Statistical Approach

A sequential statistical approach was applied to optimizing the fermentation medium of epothilones（Epos） production by means of a mutant which was obtained by treating polyangium cellulosum ATCC 15384 with nitrite and ultraviolet. The effects of different carbon sources and nitrogen sources on the fermentation medium were tested, and the suitable ones were selected. Then a uniform design was employed to design the experiments. A linear model was developed for identifying the significant components in fermentation medium, while a third degree polynomial model was used for studying the relationship between the concentration of the components in fermentation medium and the yield of Epos（YEPs）. A pattern search method was used for searching the optimum fermentation medium in the test space, which was as follows（g/L）： potassium nitrate 8.00, soybean peptone 17.60, potassium hydrogen phos- phate 1.00, beef extraction 6.46, yeast extraction 1.00, calcium chloride 0.25, sodium chloride 1.00 and ferric chloride 0.02. The optimum fermentation medium was expected to result in a yield of Epos（YEPs） of 2.48 mg/L. The validation experiments with the optimum medium were performed in triplicate and the average yield of Epos was 2.45 mg/L which was 7.78 times higher than that of Epos prepared without optimization.

Improvement of spergualin production by mutation and medium optimization

In order to screen a high-yield spergualin-production strain and an optimal fermentation medium, large numbers of isolates were selected after ultraviolet （UV） mutation and self-tolerant mutation of Bacillus laterosporus A7. A high-yield strain A-94-7 was obtained and the spergualin productivity was 4. 1-fold of the parent strain. The genetic stability of the high-yield strain Bacillus laterosporus A-94-7 was very good. Aider fermentation medium optimization, Bacillus laterosporus A-94-7 was able to produce 380 mg· L^-1 The spergualin productivity in Bacillus laterosporus A7 was increased 4.75-fold by mutation and medium optimization.

Optimization of Medium Composition for Production of Recombinant Calf Chymosin from Kluyveromyces lactis in Submerged Fermentation

Response surface methodology was applied to optimize medium components for production of recombinant calf chymosin by Kluyveromyces lactis GG799.The previous data indicated that the most suitable carbon source,nitrogen source,salt and vitamin were glucose,yeast extract,KH2PO4 and Ca D-Pantothenate,respectively.The concentration of four media components were optimized by using central composite design of response surface methodology.The optimum medium composition for recombinant calf chymosin production was found to contain glucose 29.84 g· L-1,yeast extract 19.85 g·L-1,KH2PO4 0.1 g·L-1 and Ca D-Pantothenate 4.49 mg·L-1.The enzyme activity of recombinant calf chymosin was 722 U· mL-1,which was in an excellent agreement with the predicted value（723 U·mL-1）.The production of recombinant calf chymosin from Kluyveromyces lactis GG799 was effectively increased by response surface methodology.

Optimization of Callus Induction Conditions from Immature Embryos of Maize under Stress

The embryos of maize(Zea mays L.)inbred lines GS02,GS07,GS08,GS11 and GS15 were used as receptor materials to optimize the receptor system from the aspects of genotype,medium components and stress(PEG6000,mannitol,salt and low phosphorus).The results showed that GS07 had the highest induction rate(95.2%).Orthogonal test analysis showed that the best combination of medium components in induction was A2B3C1D3(2),namely,the concentration of 2,4-dichlorophenoxy acetic acid(2,4-D)was 4 mg·mL^(-1),the concentration of L-Proline(L-Pro)was 0.8 mg·mL^(-1),and the concentration of silver nitrate(AgNO3)was 10 mg·mL^(-1)(or 5 mg·mL).Interestingly,we found that the optimal medium supplemented with 30 g·L^(-1)PEG6000 or 80 g·L^(-1)mannitol was suitable for antioxidant enzyme activity and malondialdehyde(MDA)content in GS07 callus.Exogenous 10 mmol·L^(-1)Ca^(2+)in the medium components with 100 mmol·L^(-1)sodium chloride(NaCl)could improve the activity of antioxidant enzymes in GS07 callus.Callus of GS07 could divide normally and grow well in medium components with 27 mg·L^(-1)KH_(2)PO_(4).This study enhanced the adaptability of maize callus to stress and optimized the culture conditions.

Fuel ethanol production using novel carbon sources and fermentation medium optimization with response surface methodology

In this study,ethanol production abilities of the novel carbon sources:sodium and calcium gluconate in different minimal and rich media were compared with glucose using Escherichia coli KO11.The strain produced higher ethanol yield in the rich medium Luria-Bertani(LB)than the other two minimal media:corn steep liquor(CSL)and M9 for two substrates(sodium and calcium gluconate).Additionally,higher ethanol yields were achieved when the strain was grown in LB and M9 medium with calcium gluconate than sodium gluconate,while the ethanol yields were similar when both sodium and calcium gluconate were added into CSL medium respectively.Response surface methodology was used to optimize the fermentation medium components for enhancing ethanol production using strain E.coli KO11 in CSL medium with calcium gluconate as the substrate in batch culture.The concentration of the potassium phosphate buffer is the only significant factor among five factors considered.A quadratic model was developed to describe the relationship between ethanol production and the factors.The optimal conditions predicted for five factors were 14.38 g/L CSL,0.0398 g/L FeCl_(3)·6H2O,1.12 g/L MgSO_(4)·6H_(2)O,15.41 g/L(NH4)_(2)SO_(4),and 1.58/1.26 g/L KH_(2)PO_(4)/K_(2)HPO_(4)(2:1 molar ratio).The highest ethanol concentration under optimal conditions was 31.5 g/L,which was 5.6 g/L higher than that from the same fermentation concentration of calcium gluconate in LB media.The high correlation between the predicted and experimental values confirmed the validity of the model.

Accelerating the menaquinone‑7 production in Bacillus amyloliquefaciens by optimization of the biosynthetic pathway and medium components

Menaquinone-7(MK-7)has an important role in preventing diseases such as cardiovascular disease and osteoporosis.In this study,a combination strategy of strain improvement and medium optimization is investigated to increase MK-7 production in Bacillus amyloliquefaciens.Conventional breeding method was first used to modify the biosynthetic pathway to construct a MK-7 high-producing strain by atmospheric and room temperature plasma mutagenesis and protoplast fusion.The resulted strain Ba-4 with resistance to sulfaguanidine,1-hydroxy-2-naphthoic acid,menadione,2-deoxy-d-glucose and rifampicin as well as sensitive toβ-fluoropyruvate produced 73.57±1.61 mg/L of MK-7,which was 1.36 times more than that of the parent strain H.β.D.R.-5(i.e.,31.12±1.40 mg/L).Subsequently,single-factor optimization and response surface method-ology(RSM)were used to optimize the medium components for increasing MK-7 production by strain Ba-4.Strain Ba-4 produced 90.43±1.32 mg/L of MK-7 under the single-factor optimized medium.Moreover,the results of response surface methodology indicated that glycerol,soy peptone and Tween-80 had significant effects on MK-7 production,and the highest MK-7 production(i.e.,95.03±1.01 mg/L)was obtained under the optimized medium,which was 0.29 times higher than that of the initial medium.These results confirmed that the conventional breeding methods and fermenter control system are effective strategies in improving MK-7 production by B.amyloliquefaciens.

Biodecoloration of Reactive Black 5 by the methylotrophic yeast Candida boidinii MM 4035

Azo dyes are extensively used in textile dyeing and other industries. Effluents of dying industries are specially colored and could cause severe damage to the environment. The anaerobic treatment of textile dying effluents is nowadays the preferred option, but it could generate carcinogenic aromatic amines. Recently, yeasts have become a promising altemative, combining unicellular growth with oxidative mechanisms. This work reports the characterization of the first methylotrophic yeast with dye decolorizing ability, Candida boidinii MM 4035 and some insights into its decoloration mechanism. The analysis of two selected media revealed a possible two stages mechanism of Reactive Black 5 decoloration. In glucose poor media, decoloration is incomplete and only the first stage proceeds, leading to the accumulation of a purple compound. In media with higher glucose concentrations, the yeast is able to decolorize totally an initial concentration of 200 mg/L. The entire process is co-metabolic, being largely dependent on glucose concentration but being able to proceed with several nitrogen sources. Manganese dependent peroxidase but not laccase activity could be detected during decoloration. Aromatic amines do not accumulate in culture media, supporting an oxidative decoloration mechanism of unknown ecophysiological relevance.