Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.     

Comparisons of existing pretreatment,saccharification, and fermentation processes for butanol production from agricultural residues

Some of the most recent, relevant, industrial and academic contributions made in the field of butanol production are reviewed here. The focus on butanol is due to the growing demand for non‐fossil biofuels. In addition, butanol can be mixed with fossil fuels or can be used alone, allowing an alternative to gasoline. Butanol can be synthesised biologically using sugars extracted from biomass such as agricultural waste. This agricultural waste must be pretreated before it is suitable for sugar extraction. Following this stage, enzymatic hydrolysis is employed, before performing fermentation using microorganisms. This article summarises some of the economical methods such as simultaneous saccharification and fermentation (SSF). Different pretreatment and saccharification processes were compared. Acid pretreatment and saccharification achieved the highest sugar concentrations from wheat straw. Monoethanolamine pretreatment achieved highest sugars from hardwood. Comparisons and analysis of different types of fermentation processes illustrated that immobilised reactor provided the best butanol rate of production. Integration of fermentation with product removal process improved butanol production in immobilised reactor. Gas stripping method was illustrated to be the product removal process. © 2011 Canadian Society for Chemical Engineering     

Production and characterization of a milk-clotting protease in the crude enzymatic extract from the newly isolated Thermomucor indicae-seudaticae N31: (Milk-clotting protease from the newly isolated Thermomucor indicae-seudaticae N31)

Microbial rennet-like milk-clotting enzymes are aspartic proteinases that catalyze milk coagulation, substituting calf rennet. Crude enzymatic extract produced by the thermophilic fungus, Thermomucor indicae-seudaticae N31, on solid state fermentation (SSF) using wheat bran, exhibited high milk-clotting activity and low proteolytic activity after 24 h of fermentation. Highest milk-clotting activity (MCA) was at pH 5.7, at 70 °C and in 0.04 M CaCl₂; it was stable in the pH range 3.5–4.5 for 24 h and up to 45 °C for 1 h. MCA was highly inhibited by pepstatin A. Hydrolytic activity profile of the crude enzymatic extract on whole bovine casein, analyzed by gel electrophoresis (Urea–PAGE) and RP-HPLC revealed low proteolytic action towards casein fractions and a peptide profile similar to the one obtained with commercial Rhizomucor miehei protease (Hannilase).     

Production of protein and metabolites by yeast grown in solid state fermentation: present status and perspectives

Culture conditions for the generation of products using yeast have been optimized for fermentative processes in industry involving predominantly submerged medium (SmF). However, solid‐state fermentation (SSF) is now a realistic alternative system for the production of recombinant proteins and metabolites of interest in the market, with great potential in biofuels production, food, chemical and pharmaceutical industries. One of the main advantages of SSF over SmF is the reduction of downstream expenses. Also, the use of artificial and very cheap solid supports for yeast SSF such as polyurethane foam or amberlite helps with study of the physiology of such systems. This mini‐review makes an overview of previous research and emphasizes the major physiological advantages of yeast SSF that can be used for new processes and product development and stresses the need for integrated approaches between adaptive evolution and high‐throughput genetic analysis. © 2015 Society of Chemical Industry     

Feasible process development and techno-economic evaluation of paper sludge to bioethanol conversion: South African paper mills scenario

Paper sludge samples collected from recycling mills exhibited high ash content in the range of 54.59%–65.50% and glucose concentrations between 21.97% and 31.11%. Washing the sludge reduced the total ash content to between 10.7% and 19.31% and increased the concentration of glucose, xylose and lignin. Samples were screened for ethanol production and fed-batch simultaneous saccharification and fermentation (SSF) was optimised for the washed samples that resulted in highest and lowest ethanol concentrations. Maximum ethanol concentrations of 57.31 g/L and 47.72 g/L (94.07% and 85.34% of the maximum theoretical yield, respectively) was predicted for high and low fermentative potential samples, respectively, and was experimentally achieved with 1% deviation. A generic set of process conditions were established for the conversion of high ash-containing paper sludge to ethanol. Techno-economic analysis based on three different revenue scenarios, together with Monte Carlo analysis revealed 95% probability of achieving IRR values in excess of 25% at a paper sludge feed rate of 15 t/d. Feed rates of 30 t/d and 50 t/d exhibited a cumulative probability of 100%. This study presents the technical feasibility and economic viability of paper mills expansion towards bioethanol production from paper sludge.     

Strategy for preventing bacterial contamination by adding exogenous ethanol in solid-state semi-continuous bioethanol production

A strategy for preventing reduction of ethanol yield in fermentation caused by bacterial contamination was developed. In solid-state ethanol fermentation in which saccharification, fermentation and ethanol recovery are performed simultaneously, the addition of exogenous ethanol to the fermentation mixture at the start of fermentation at 50 g kg(-1) prevented contamination, and the ethanol yield reached 0.50 g g(-1).     

Penicillium commune spore production in solid‐state fermentation of coffee pulp at laboratory scale and in a helical ribbons rotating reactor

Penicillium commune was grown on coffee pulp (CP) by solid‐state fermentation (SSF). The effects of the duration of CP thermal treatment and the effects of incubation temperature on spore production yield were studied at laboratory scale. The effect of mixing during fermentation was assayed at pilot plant scale in a 70 L stainless steel non‐aseptic reactor equipped with helical ribbons for mixing solids. For thermal treatments of CP at 121 °C for 10, 20, 30 and 40 min, no significant difference in spore production yield was observed. Maximum sporulation yield was found at 25 °C; when the incubation temperature was higher than 30 °C, the sporulation yield decreased significantly. A spore production yield of 3.7 × 10⁹ spores g^?1 dry CP was obtained when continuous mixing (0.25 rpm) was used at pilot plant scale; however, a decrease in spore yield (1.4 × 10⁹ spores g^?1 dry CP) was observed under static conditions. Spore production was not affected when a scale factor between 79 and 105 was assayed from laboratory to pilot plant; at this level, the productivity obtained was 3.1 × 10⁷ spores g^?1 dry CP h^?1. This value is similar to that found in other reports using natural substrates but working at a smaller scale. Copyright © 2006 Society of Chemical Industry     

Cell growth and Trametes versicolor laccase production in transformed Pichia pastoris cultured by solid‐state or submerged fermentations

BACKGROUND: Growth kinetics of Pichia pastoris and heterologous expression of Trametes versicolor laccase were compared. This is the first study of its kind between solid‐state yeast cultures done on polyurethane foam (PUF) and submerged liquid fermentations (SmF). RESULTS: The maximum values of biomass were similar for SSF (solid‐state fermentation) and SmF experiments when the BOD (biochemical oxygen demand) was lower than 100 g L^?1. For higher BOD levels, the maximum values of biomass were 55 g L^?1 (SSF) and 35 g L^?1 (SmF). Micrographs of PUF preparations showed yeast growing within liquid lamellae, thinner than 100 µm, forming large horizontal aggregates. Yeast aggregates were much smaller in SmF than in SSF experiments; however, laccase expression was lower in PUF than in SmF, unless the methanol concentration was increased to 63 g L^?1, which was inhibitory only to the SmF system. CONCLUSION: The results show that oxygen mass transfer is more efficient in SSF, which is related to the higher area/volume ratio compared with SmF. Induction differences may also be due to hindered diffusion of methanol within large yeast aggregates. Copyright © 2009 Society of Chemical Industry     

花土沟油田断层封堵性研究

花土沟油田区内断层相当发育,断层的封堵性判定对油田开发方案的制定至关重要。在此以花土沟油田东14断层为例,运用泥岩涂抹系数作为评价参数,类干扰试井和示踪剂监测作为论证方法,定量分析了其封堵性。对开展区域断层的封堵性研究具有借鉴作用。     

Steam pretreatment of dilute H2SO4-impregnated wheat straw and SSF with low yeast and enzyme loadings for bioethanol production

Conversion of lignocellulosic material to monomeric sugars and finally ethanol must be performed at low cost, i.e. with limited consumption of chemicals, yeast and enzymes while still reaching high yields, if it is to compete with other fuel conversion processes. The objective of this study was thus to investigate ethanol production from steam-pretreated wheat straw by simultaneous saccharification and fermentation (SSF). The concentration of sulphuric acid in the impregnation liquid prior to pretreatment was kept low, 0.2%, and SSF was performed at low enzyme loadings, 3–14 FPU g⁻¹ water-insoluble solids (WIS), and a low yeast concentration, 2 g L⁻¹. The pretreatment conditions were optimised to give the highest overall glucose and xylose recovery after enzymatic hydrolysis of the residual WIS. The highest recovery of glucose (102%) and xylose (96%) was obtained after pretreatment at 190 °C for 10 min. Achieving high yields of glucose and xylose with the same pretreatment conditions is unusual and makes wheat straw a highly suitable raw material for bioethanol production. SSF was performed on whole slurry from straw pretreated under the optimal conditions. A high overall ethanol yield, 67% of the theoretical based on glucose in the raw material, was obtained.