Effect of pretreatment of molasses and posttreatment of fermented broth in industrial production of ethanol

The aim of preclarification is to minimize sludge going to yeast separators. This purpose is partially fulfilled. However, it has been measured during the plant trial runs that preclarification does not noticeably improve fermentation. The aim of postclarification is to minimize sludge going to distillation. This purpose is well served as noted from the fact that cycle run of distillation columns using postclarification is three times longer (9–12 mo) as compared to the normal one (3–4 mo).     

Conversion of municipal solid waste into carboxylic acids by anaerobic countercurrent fermentation

Municipal solid waste (MSW) and sewage sludge (SS) were combined and anaerobically converted into carboxylate salts by using a mixed culture of acid-forming microorganisms. MSW is an energy source and SS is a source of nutrients. In this study, MSW and SS were combined, so they complemented each other. Four fermentors were arranged in series for a countercurrent fermentation process. In this process, the solids and liquid were transferred in opposite directions, with the addition of fresh biomass to fermentor 1 and fresh liquid media to fermentor 4. An intermediate lime treatment of solids exiting fermentor 3 before entering fermentor 4 was applied to improve the product acid concentration from the untreated MSW/SS fermentations. All fermentations were performed under anaerobic conditions at 40°C. Calcium carbonate was added to neutralize the carboxylic acids and to control the pH. Iodoform was used as a methanogen inhibitor. Carboxylic acid concentration and gas composition were determined by gas chromatography. Substrate conversion was measured by volatile solids loss, and carboxylic acid productivity was calculated as the function of the total carboxylic acids produced, the amount of liquid in all fermentors, and time. The addition of intermediate lime treatment increased product concentration and conversion by approx 30 and 15%, respectively. The highest carboxylic acid concentrations for untreated MSW/SS fermentations with and without intermediate lime treatment were 22.2 and 17.7 g of carboxylic acid/L of liquid, respectively. These results confirm that adding a treatment step between fermentor 3 and fermentor 4 will increase the digestibility and acid productivity of the fermentation.     

Evaluation of optimization techniques for an extractive alcoholic fermentation process

The mathematical optimization of a continuous alcoholic fermentation process combined with a flash column under vacuum was studied. The objective was to maximize % yield and productivity in the fermentor. The results using surface response analysis combined with modeling and simulation were compared withy those obtained when the problem was written as a nonlinear programming problem and was solved with a successive quadratic programming (SQP) technique. Two process models were evaluated when the process was optimized using the SQP technique. The first one is a deterministic model, whose kinetic parameters were experimentally determined as functions of the temperature, and the second is a statistical model obtained using the factorial design technique combined with simulation. Although the best result was the one obtained using the rigorous model, the values for productivity and % yield obtained using the simplified model are acceptable, and these models can be used when the development of a rigorous model is excessively difficult, slow, or expensive.     

Ethanol removal from fermentation broth by gas membrane extraction

A new type of membrane extraction for in situ removal of ethanol from fermentation broth is presented. Aqueous solutions of propylene glycol are used as extractants. The extractatant and the broth are separated by a microporous hydrophobic membrane which is not penetrated by the broth or by the extractant. As a consequence a thin gas layer, essentially air, is immobilised within the membrane pores and separates the two liquid phases (i.e. a gas membrane). Vapour-liquid equilibria are established at both membrane sides; because glycols reduce the ethanol content of the equilibrium vapour phase with respect to the binary system, ethanol vapours preferentially diffuse through the stagnant gas layer.     

离子排斥法测定丙酮酸发酵提取液中的丙酮酸含量

建立一种测定丙酮酸发酵液中丙酮酸含量的方法。采用有机酸离子排斥柱,TSKgel OApak-A为分析柱,TSKgel OApak-P为保护柱;柱温:40℃;流动相:4.5mmol/L H2SO4,流速0.8mL/min;检测波长:210nm。丙酮酸在42.45~2122.3mg/L范围内,峰面积与样品浓度有良好的线性关系(A=4.7278c 31.6296,r=0.9999),检出限为4.6mg/L。发酵液中丙酮酸含量在5.1%左右,丙酮酸的回收率为97.11%~99.21%。     

灵芝富碘实验中多糖含量变化的探讨

阐述了ＴＷ灵芝在液体深层培养中，进行富集碘实验过程菌丝体多糖含量的变化．实验表明，在ＴＷ灵芝液体培养中添加１０００×１０－６～８０００×１０－６浓度的碘化钾，菌丝体多糖含量为０．９２％～１．５８％．     

Process optimisation for the biosynthesis of cellulase by Bacillus PC-BC6 and its mutant derivative Bacillus N3 using submerged fermentation

This study deals with optimisation of cultural conditions for enhanced production of cellulase by Bacillus PC-BC6 and its mutant derivative Bacillus N3. Influence of different variables including incubation time, temperature, inoculum size, pH, nitrogen sources and metal ions has been studied. The optimum conditions for cellulase production were incubation period of 72 h, inoculum size 4% incubation temperature 37°C, pH 7, 0.25% ammonium sulphate, 0.2% peptone as inorganic and organic nitrogen source in case of Bacillus PC-BC6. In case of mutant Bacillus N3, optimal conditions were incubation period of 48 h, incubation temperature 37°C, inoculum size 3%, pH 7, 0.2% ammonium chloride and 0.15% yeast extract. Presence of MnSO₄ and CaCl₂ enhances the enzyme production by Bacillus PC-BC6 and mutant Bacillus N3, respectively. This study was innovative and successful in producing cellulase economically by using cheap indigenous substrate Saccharum spontaneum.     

新型发酵蔬菜制品乳酸菌发酵剂的筛选研究

从榨菜等一些自然腌制蔬菜制品中分离得到一些乳酸菌菌株，通过细胞形态及生理学特性观察研究，初步筛选出Lactobacillus 8株菌株，并进一步通过发酵产酸和细胞生长比较实验得到3株乳酸菌菌株Lact，2，Lact．6和Lact．8，通过菌株间不同配比和发酵榨菜验证实验，最后确定了榨菜发酵制品的最适发酵剂为Lact．2和Lact.8，最佳配比为1：1．     

Mutagenesis and analysis of mold Aspergillus niger for extracellular glucose oxidase production using sugarcane molasses

Aspergillus niger ORS-4.410, a mutant of A. niger ORS-4, was generated by repeated ultraviolet (UV) irradiation. Analysis of the UV treatment dose on wild-type (WT) A. niger ORS-4, conidial survival, and frequency of mutation showed that the maximum frequency of positive mutants (25.5%) was obtained with a 57% conidial survival rate after the second stage of UV irradiation. The level of glucose oxidase (GOX) production from mutant A. niger ORS-4.410 thus obtained was 149% higher than that for WT strain A. niger ORS-4 under liquid culture conditions using hexacyanoferrate (HCF)-treated sugarcane molasses (TM) as a cheaper carbohydrate source. When subcultured monthly for 24 mo, the mutant strain had consistent levels of GOX production (2.62±0.51 U/mL). Mutant A. niger ORS-4.410 was markedly different from the parent strain morphologically and was found to grow abundantly on sugarcane molasses. The mutant strain showed 3.43-fold increases in GOX levels (2.62±0.51 U/mL) using HCF-TM compared with the crude form of cane molasses (0.762±0.158 U/mL). The results reported herein were obtained while the author was working at the Department of Biotechnology, Indian Institute of Technology, Roorkee-247667, India.     

Ethanol production from dilute-acid softwood hydrolysate by co-culture

Dilute-acid softwood hydrolysate, with glucose and xylose as the dominant sugars was fermented to ethanol by co-cultures. The strains used include Saccharomyces cerevisiae 2.535 (1#), Pachysolen tannophilis ATCC 2.1662 (2#), and recombinant Escherichia coli (3#) constructed in our laboratory carrying both pdc and adhB genes derived from Zymomonas mobilis. Before fermentation, the co-cultures were adapted for five batches. Observation under light microscope showed aggregation of adapted strains, which could possibly improve their ability to degrade inhibitors. In addition, we tried to detoxify the dilute-acid softwood hydrolysate with a combined method before fermentation. Our study showed that fermentation of detoxified hydrolysate by adapted co-culture (1# + 2@) generated an exceptionally high ethanol yield on total sugar of 0.49 g/g, corresponding to 96.1% of the maximal theoretical value after 48h; fermentation of detoxified hydrolysate by adapted co-culture (1# + 3#) is faster (24h) and could reach a high ethanol yield (0.45 g/g total sugar). These experiments suggest that both adaptation and detoxification significantly improve hydrolysate fermentation and ethanol production.