Lactic acid production from submerged fermentation of broken rice using undefined mixed culture

The present work aimed to characterize and optimize the submerged fermentation of broken rice for lactic acid (LA) production using undefined mixed culture from dewatered activated sludge. A microorganism with amylolytic activity, which also produces LA, Lactobacillus amylovorus, was used as a control to assess the extent of mixed culture on LA yield. Three level full factorial designs were performed to optimize and define the influence of fermentation temperature (20–50?°C), gelatinization time (30–60 min) and broken rice concentration in culture medium (40–80 g L^?1) on LA production in pure and undefined mixed culture. LA production in mixed culture (9.76 g L^?1) increased in sixfold respect to pure culture in optimal assessed experimental conditions. The optimal conditions for maximizing LA yield in mixed culture bioprocess were 31?°C temperature, 45 min gelatinization time and 79 g L^?1 broken rice concentration in culture medium. This study demonstrated the positive effect of undefined mixed culture from dewatered activated sludge to produce LA from culture medium formulated with broken rice. In addition, this work establishes the basis for an efficient and low-cost bioprocess to manufacture LA from this booming agro-industrial by-product.     

添加剂对水稻秸秆实地混合厌氧发酵产甲烷系统的作用

为提高水稻秸秆利用效率,改进水稻秸秆实地混合厌氧发酵产甲烷技术,本研究开展了添加剂在混合厌氧发酵系统的应用研究。试验选取水稻秸秆和猪粪作为发酵原料,通过分别添加不同的浓度的吐温20和腐植酸,测定甲烷的产气量和浓度、秸秆的降解和土壤肥力的变化,以揭示添加剂类型及其浓度对水稻田实地甲烷生产系统的影响。结果表明:添加剂的掺入并未影响产气的动态变化趋势,但显著地促进产气和提高产气浓度,整体效果由高到低为腐植酸吐温20对照,其中经腐植酸处理的产气量和产气浓度对照相比分别提高了50. 73%和24. 55%。添加剂的掺入有利于水稻秸秆纤维素和半纤维素的降解,但对木质素没有显著影响;其中以0. 15 g/L腐植酸和0. 30 g/L吐温20的降解率最高,相较于对照其纤维素降解率均提高了22. 11%,半纤维素降解率分别提高了107. 13%和98. 39%。添加剂的掺入能显著增加土壤肥力,以0. 15 g/L腐植酸和0. 30 g/L吐温20处理水平的效果最优,相较于对照,其土壤有机质分别增加了29. 63%和23. 72%,全氮分别增加了52. 32%和42. 38%,全磷分别增加了83. 33%和57. 14%。     

Effect of pH oscillations on a competing mixed culture

Two microorganisms, E. coli and S. cerevisiae, competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a Chemostat. Pure culture experiments found S. cerevisiae to be insensitive to pH between 5 and 4.3 with a maximum specific growth rate (mu(max)) of 0.4/hr; while mu(max) of E. coli decreased from 0.6 h(-1) at pH 5 to 0.1 h(-1) at pH 4.3. Steady-state and cross-inoculation chemostat runs at a dilution rate of 0.17 h(-1) confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D =0.17 h(-1) with 1 g per liter glucose feed. The 16 h/16 h cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 h pH 5/14 h pH 4.3 cycle was found to be stable with smaller yeast concentrations. A 6 h/6 h cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus, varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.     

Effect of controlled substrate feeding on butyric acid production byClostridium tyrobutyricum

Summary Production of butyric acid from wheat flour hydrolysate was studied withClostridium tyrobutyricum. The mode of substrate supply was found a key parameter for fermentation performance as large improvements were obtained by feeding with a non-limiting supply of substrate. With this procedure, increases in product concentration and productivity but also in selectivity and yield for butyrate were obtained. Substrate feeding controlled by the rate of gas production was found preferable to constant rate feeding for reason of convenience and flexibility. In these conditions, a butyrate concentration of 62.8 gl^–1 was obtained with a productivity of 1.25 gl^–1 h^–1, a selectivity of 91.5% and a yield of 0.45 g per g of glucose.     

Hyper-thermal acid hydrolysis and adsorption treatment of red seaweed,Gelidium amansii for butyric acid production with pH control

Bioprocess and Biosystems Engineering - Optimal hyper-thermal (HT) acid hydrolysis conditions for Gelidium amansii were determined to be 12% (w/v) seaweed slurry content and 144 mM H2SO4...     

降解水稻秸秆兼抑制水稻纹枯病菌多功能复合菌系的构建

目的针对稻草直接还田需要,构建能够高效降解水稻秸秆同时又能抑带l水稻纹枯病菌的多功能复合菌系。方法通过将具有高效降解纤维素的天然复合菌群与具有抑制水稻纹枯病菌效果的菌株组合,构建多功能复合菌系;采用失重法检测该复合菌系对水稻秸杆的腐解作用,荧光定量PER法检测其对水稻纹枯病菌的抑制效果。结果成功地构建了一组多功能复合菌系,腐解12d后,水稻秸秆干物质总失重率为41．4％,其中半纤维素降解率为59．5％,纤维素降解率为52．5％,木质素降解率为15．3％,腐解过程中平均CMC酶活为8．1IU／g。该复合菌系对水稻纹枯病菌的抑制效果明显,发酵40d后对水稻纹枯病菌的抑制率为27．1％,对照组抑制率为2．7％。结论该复合菌系能高效降解水稻秸秆,同时又能较好地抑制水稻纹枯病菌,适宜在水稻秸秆直接还田过程中使用。     

Effect of nickel on methane production and butyric acid utilization in a downflow fixed-film reactor

Summary Butyric acid conversion by a mixed methanogenic population in a pilot scale anaerobic downflow fixed-film reactor (DFFR), treating a cheese factory effluent was increased by the addition of nickel (30 mg/l NiCl₂. 6H₂O). The butyric acid concentration dropped abruptly (2300 to 150 mg/l) when the reactor was fed with Ni (II). Furthermore, when running two lab. scale DFFRs butyric acid utilization and methane production were slightly higher within the reactor supplemented with nickel than in the control reactor (without nickel).     

Effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes in continuous culture

Summary The effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes from glucose was investigated in a microaerobic continuous culture. At a dilution rate of 0.20 h^–1 and a fixed oxygen uptake rate (OUR) of 31.5 mmol l^–1 h^–1 the biomass concentration increased with pH ranging from 5.0 to 7.0, while the specific ATP requirement of the cells decreased. In the pH range 5.5–6.5 the product concentration (butanediol + acetoin) was maximal and nearly constant. However, the specific production continuously declined with increasing pH. Experiments with addition of acetic acid showed that the various effects of pH are due to inhibition of the by-product acetic acid on cell growth. The strength of the acetic and inhibition depended only on the concentration of its undissociated form [HAc]. The biomass concentration and the specific OUR were also only functions of [HAc], irrespective of the pH. Although the specific ATP requirement (q ATP) strongly depended on the pH, [HAc] at constant pH. Offprint requests to: W.-D. Deckwer     

Effect of growth supplements and whey pretreatment on butyric acid production by Clostridium butyricum

Improved production of butyrate (up to 19 g/l) from whey by Clostridium butyricum was achieved by adding either yeast extract (5 g/l) or biotin (50 g/l). Hydrolysed lactose and proteolysed whey were less effective even with added biotin.The authors are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, Bratislava 812 37, Slovakia     

Kinetic study of pH effects on biological hydrogen production by a mixed culture

The effect of pH on anaerobic hydrogen production was investigated under various pH conditions ranging from pH 3 to 10. When the modified Gompertz equation was applied to the statistical analysis of the experimental data, the hydrogen production potential and specific hydrogen production rate at pH 5 were 1,182 ml and 112.5 ml/g biomass-h, respectively. In this experiment, the maximum theoretical hydrogen conversion ratio was 22.56%. The Haldane equation model was used to find the optimum pH for hydrogen production and the maximum specific hydrogen production rate. The optimum pH predicted by this model is 5.5 and the maximum specific hydrogen production rate is 119.6 ml/g VSS-h. These data fit well with the experimental data (r2=0.98).     

培养条件下二氯喹啉酸对土壤微生物群落结构的影响

为探讨除草剂二氯喹啉酸对土壤微生物群落结构的影响,在25℃黑暗培养条件下,采用磷脂脂肪酸法(Phospholipid Fatty Acid,PLFA)分析了二氯喹啉酸(0对照、83.3和166.6μg/kg干土)处理对淹水和不淹水水田土壤微生物群落结构的影响。结果表明,在实验处理的60 d内,不淹水水田土壤在83.3μg/kg二氯喹啉酸处理后对土壤微生物生物总量、细菌生物量及真菌生物量有抑制作用,而166.6μg/kg二氯喹啉酸处理后各生物量指标均显著增加,但是两种浓度处理均使土壤真菌/细菌比值下降,说明二氯喹啉酸处理会使不淹水水田土壤微生物稳定性下降;淹水水田土壤在83.3μg/kg二氯喹啉酸处理下,对土壤微生物生物总量和真菌生物量有促进作用,对细菌生物量有一定的抑制作用,166.6μg/kg二氯喹啉酸处理对土壤微生物生物总量、细菌及真菌生物量均有促进作用,从真菌/细菌比值上看,不同浓度处理与对照无显著差异,说明二氯喹啉酸对淹水生物稳定性无明显干扰。PLFA主成分分析表明,不同浓度处理的两种土壤微生物群落均以含14∶0、15∶0、16∶0和18∶2n6c的微生物为优势种群。     

Fixed-bed fermentation of rice straw and chicken manure using a mixed culture of marine mesophilic microorganisms

A mixture of rice straw (80%) and chicken manure (20%) was pretreated and fermented to carboxylic acids by using a mixed culture of marine mesophilic microorganisms. Two sets of four fermentors, built from PVC pipes, were used for both biomass pretreatment and fermentation. Four 1L fermentors (F1-F4) were arranged in series, where liquid fermentation products were transferred from one fermentor to the other, to form a train. A liquid volume of 10mL and 15mL were transferred every four days for Trains A and B, respectively. The maximum total acid concentration for F1 in Train A was 34.2g/L and the maximum acid concentration in F2-F4 was approximately 44g/L. The maximum total acid concentration in F1 in Train B was 30.5g/L and the maximum acid concentration in F2-F4 was approximately 48g/L. The conversion in each of the fermentors in Train A varied from 0.821 to 0.879g VS digested/g VS fed and the yield was in the range 0.489-0.609g total acids/g VS fed. The conversion and yield in Train B were 0.741-0.914g VS digested/g VS fed and 0.563-0.669g total acids/g VS fed, respectively. The continuum particle distribution model (CPDM) predicted acid concentrations and retention times in the fixed-bed fermentation system with R(2) of 0.67-0.84 in Trains A and B.     

Influence of pH and undissociated butyric acid on the production of acetone and butanol in batch cultures of Clostridium acetobutylicum

Summary The kinetics of growth and acid and solvent production are examined in batch fermentation of Clostridium acetobutylicum at pH between 4.5 and 6.0. At the lower pH, growth occurs in two consecutive phases and solvents are the main excreted metabolites. At the higher pH, there is a single growth phase with only acid formation. The influence of the pH can be correlated with a critical role of the concentration of undissociated butyric acid in the medium: cellular growth is inhibited above 0.5 g/l and solvent production starts at an undissociated acid level of 1.5 g/l. Reducing the intracellular acid dissociation by lowering the intracellular pH also favours the production of acetone and butanol.     

Studies on potential effects of fumaric acid on rumen microbial fermentation,methane production and microbial community

The greenhouse gas methane (CH₄) contributes substantially to global climate change. As a potential approach to decrease ruminal methanogenesis, the effects of different dosages of fumaric acid (FA) on ruminal microbial metabolism and on the microbial community (archaea, bacteria) were studied using a rumen simulation technique (RUSITEC). FA acts as alternative hydrogen acceptor diverting 2H from methanogenesis of archaea towards propionate formation of bacteria. Three identical trials were conducted with 12 fermentation vessels over a period of 14 days. In each trial, four fermentation vessels were assigned to one of the three treatment groups differing in FA dosage: low fumaric acid (LFA), high fumaric acid (HFA) and without FA (control). FA was continuously infused with the buffer. Grass silage and concentrate served as substrate. FA led to decreases in pH and to higher production rates of total short chain fatty acids (SCFA) mediated by increases in propionate for LFA of 1.69 mmol d^?1 and in propionate and acetate production for HFA of 4.49 and 1.10 mmol d^?1, respectively. Concentrations of NH₃-N, microbial crude protein synthesis, their efficiency, degradation of crude nutrients and detergent fibre fraction were unchanged. Total gas and CH₄ production were not affected by FA. Effects of FA on structure of microbial community by means of single strand conformation polymorphism (SSCP) analyses could not be detected. Given the observed increase in propionate production and the unaffected CH₄ production it can be supposed that the availability of reduction equivalents like 2H was not limited by the addition of FA in this study. It has to be concluded from the present study that the application of FA is not an appropriate approach to decrease the ruminal CH₄ production.     

Effect of culture medium pH on bacterial gellan production.

The effect of the initial pH of the culture medium used in the production of the exopolysaccharide gellan by the bacterium Pseudomonas species ATCC 31461, when glucose or corn syrup served as the carbon source, was investigated. With glucose as the carbon source, exopolysaccharide formation was highest after 72 h of growth when the initial pH of the culture medium was 6.8 to 7.4. Polysaccharide production by the bacterial cells grown on corn syrup for 72 h was maximal when the initial pH of the medium was 7.0 or 7.2. Cell weights of the strain after 72 h tended to be higher for the glucose-grown cells than for the corn syrup-grown cells.     

Effect of rice straw additions on production of organic acids in a flooded soil

Summary Disposal of rice straw through soil incorporation may contribute to anaerobic fermentation processes producing concentrations of organic acids which are toxic to rice plants. The present studies were conducted to determine the kind, amount, and time of production of organic acids as a function of rice straw additions (0, 0.25, and 0.5 per cent of soil weight), and temperature (10, 20, and 30°C). Nine samples were taken at 5, and 10 day intervals for 60 days to measure concentrations of organic acids.Only acetic acid was detected in the incubated soil with rice straw added. The amount and peak production of acetic acid increased with the rate of straw added and temperature. Acetic acid concentrations varied between 10.6 and 22.7 eq/20 g soil, and the peak production occurred between 15 and 20 days after incubation. Organic acids were not found in sufficient amounts to affect the growth of rice plants grown in soils that were not previously puddled or in a reduced state.Contribution from the Department of Agronomy and Range Science, University of California, Davis, California 95616.Contribution from the Department of Agronomy and Range Science, University of California, Davis, California 95616.     

Bio-active composts from rice straw enriched with rock phosphate and their effect on the phosphorous nutrition and microbial community in rhizosphere of cowpea

Composts were produced from rice straw enriched with rock phosphate and inoculated with Aspergillus niger, Trichoderma viride and/or farmyard manure (FYM). The resulting composts were evaluated as organic phosphate fertilizers for cowpea plants in pot experiments. The results showed that the maximum amount of soluble phosphorous (1000 ppm) was produced in composts inoculated with A. niger+T. viride with or without FYM. Any of the produced composts was much better than superphosphate fertilizer in providing the growing cowpea plants with phosphorous. Fertilization of the cowpea plants with the compost inoculated with FYM+A. niger+T. viride resulted in maximum amount of phosphorous uptake (295 ppm). The highest phosphate dissolving fungi numbers in rhizosphere soils of cowpea plants were obtained after fertilization with composts which received A. niger and T. viride treatments, while the highest phosphate dissolving bacterial numbers were found after fertilization with composts which received FYM treatments.     

秸秆还田方式对东北水稻土理化性质及微生物群落的影响

【目的】研究秸秆还田方式对东北黑土理化性质及微生物群落的影响。【方法】试验周期为2019年12月至2021年10月,秸秆还田采用2种方式： 秸秆直接还田+微生物菌剂WJ(strawdirect return+microbial agent WJ;MD),秸秆堆肥还田+微生物菌剂WJ(straw compost return +microbial agent WJ;MC)。分析土壤肥力、酶活和微生物群落。【结果】分析两种方式土壤有机质(SOM)、腐殖酸(HS)和富里酸有机碳(FA-C)含量,发现秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ分别增加2.28g/kg、7.82g/kg和5.26g/kg。土壤铵态氮(NH4⁺-N)、速效磷(AP)略高于秸秆堆肥还田+微生物菌剂WJ,均在6月份达到峰值。胡敏酸有机碳(HA-C)含量下降。此外,土壤脲酶、转化酶、纤维素酶活性和碱性磷酸酶活性对比发现,秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ分别高8.55%、15.46%、4.35%和6.19%。高通量测序结果显示,秸秆直接还田+微生物菌剂WJ中细菌和真菌的多样性均比秸秆堆肥还田+微生物菌剂WJ丰富。其中Anaerolinea、Bacteroidetes、Pseudomonas为优势细菌,Tausonia、Mrakia、Mrakiella为优势真菌。【结论】秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ更有利于土壤有机质、腐殖酸、土壤酶活性和微生物多样性的增加,这说明秸秆添加WJ菌剂直接还田可以减少有机养分的流失,保持田间土壤肥力。     

Diversity of microbial communities in open mixed culture fermentations: impact of the pH and carbon source

Anaerobic fermentation by an open mixed culture was investigated at different pH values (4–8.5) and with three substrates (glucose, glycerol and xylose). The populations established in each condition were assessed by denaturing gradient gel electrophoresis analysis of the 16S ribosomal RNA gene fragments. The fermentation pattern and the composition of the microbial population were also evaluated when operational variations were imposed (increase of substrate concentration or introduction of a second substrate). The experimental results demonstrated that at low and high pH values, a clearly different fermentation pattern was associated with the dominance of a specialised group of clostridiae. At intermediate pH values, the product spectrum was rather variable and seemed to be sensitive to variations in the microbial community. Different substrates resulted in the establishment of different microbial communities. When fed with a mixture of two substrates, mixotrophic microorganisms (capable of degrading both substrates) were found to overgrow the originally dominant specialists. Overall, the experiments have shown that some operational variables have a clear impact on the fermentation pattern and on the population established. However, a uniform relationship between the process characteristics (associated to a metabolic response) and the microbial population present is not always possible. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.