Aerobic submerged fermentation by acetic acid bacteria for vinegar production: Process and biotechnological aspects

Strictly aerobic acetic acid bacteria (AAB) have a long history of use in fermentation processes, and the conversion of ethanol to acetic acid for the production of vinegar is the most well-known application.At the industrial scale, vinegar is mainly produced by submerged fermentation, which refers to an aerobic process in which the ethanol in beverages such as spirits, wine or cider is oxidized to acetic acid by AAB. Submerged fermentation requires robust AAB strains that are able to oxidize ethanol under selective conditions to produce high-titer acetic acid. Currently submerged fermentation is conducted by unselected AAB cultures, which are derived from previous acetification stocks and maintained by repeated cultivation cycles.In this work, submerged fermentation for vinegar production is discussed with regard to advances in process optimization and parameters (oxygen availability, acetic acid content and temperature) that influence AAB activity. Furthermore, the potential impact arising from the use of selected AAB is described.Overcoming the acetification constraints is a main goal in order to facilitate innovation in submerged fermentation and to create new industry-challenging perspectives.     

Simultaneous amylase production,raw cassava starch hydrolysis and ethanol production by immobilized Aspergillus awamori and Saccharomyces cerevisiae in a novel alternating liquid phase–air phase system

As a solution to the problems of mass transfer limitation in submerged cultures and scale up of solid-state/liquid-surface cultures, an alternating liquid phase–air phase bioreactor was developed. It consisted of a bioreactor equipped with a siphon system and a reservoir. Aspergillus awamori was immobilized in loofa sponge inside the bioreactor and culture broth was pumped from the reservoir into the bioreactor. Each time the culture broth level reached a critical level, the broth automatically siphoned back into the reservoir. Thus the immobilized cells were alternatingly submerged and exposed to air. The duration of each phase was controlled by the pumping rate and with an on-off timer. During amylase production from soluble starch and raw cassava starch, the optima ratios of the liquid to air phases were 12 h : 12 h and 3 h : 6 h respectively. Saccharomyces cerevisiae IR2 was immobilized in the reservoir and the system was used for simultaneous amylase production, hydrolysis and ethanol production from raw cassava starch. The process was very stable for more than 7 batches with high ethanol yield of 0.46 g-ethanol/g-starch and productivity of 1.73 g-ethanol/L/h. These values are high, the system can be scaled up, and thus it has many potential applications.     

Secondary productivity (3H-Leucine and 3H-Thymidine incorporation), abundance and biomass of the epiphytic bacteria attached to detritus of Typha domingensis pers. in a tropical coastal lagoon

Senescent, naturally dried leaves of Typha domingensis were incubated inthe littoral region of a coastal lagoon and epiphytic bacterial volume,abundance, biomass and secondary productivity were measured during 127 daysof decomposition. The peak of cell abundance was registered at t =127 days when expressed per leaf surface area (10.07×10⁷cells cm^-2; 7.26 µgC cm^-2), and at t= 26 days when expressed per biofilm dry mass (38.10 ×10⁷ cells (mgDM biofilm)^-1, 30.52 µgC(mgDM biofilm)^-1). The highest values of bacterial biovolumesand lower turnover time were usually obtained in the beginning of thecolonization. Leu:Tdr ratios were also higher in the beginning of thecolonization, when bacterial community presented unbalanced metabolism.Consequently, the highest discrepancies between the bacterial secondaryproduction estimated by leu and Tdr incorporation were observed in the first2 days of decomposition. On average, the bacterial secondary productivityestimated by leu incorporation was 2.1 times higher than the valuesestimated by Tdr incorporation when the empirical factor for Tdr wasobtained from the relationship between Tdr and biomass increment. Thisdifference increased to 4.2 when the empirical factor was obtained from therelationship between Tdr and cell numbers increment. An average of bothmethods (0.0037 to 0.1397 µgC cm^-2 h^-1)produced results that fall within the range reported in the literature forepiphytic bacteria of freshwater ecosystems.     

Modeling nutrients,oxygen and critical phosphorus loading in a shallow reservoir in China with a coupled water quality – Macrophytes model

Many macrophyte-dominated clear lakes switch to a phytoplankton-dominated turbid state when the lake becomes eutrophic. An existing Yuqiao Reservoir Water Quality Model (YRWQM) and the macrophyte submodel were coupled to simulate the effect of submerged macrophytes on nutrients and dissolve oxygen cycles in a shallow reservoir in China. The level of phosphorus loading in a transition from a clear to turbid state was addressed using the integrated model. The model runs from seedling establishment until dying out, from March 1 to July 18 in 2009. The simulations were performed for a contingent range of P loadings, starting from three different initial conditions. The results indicated that the integrated model improves accuracy of predictions compared to YRWQM. The concentrations of nutrients declined slightly during the macrophyte growth period in the reservoir and dissolved oxygen increased slightly. Although nutrient concentrations increased by submerged macrophyte release during the extinction period, the effect on the nutrients was less than that of transfer with nutrient-rich water. More released nutrients may enhance increases in substantial abundance. The critical phosphorus loading level during a switch from the clear to turbid state was estimated by these scenarios. The threshold for the switch is ∼6.1 mgP m⁻² d⁻¹ with an initial total phosphorus concentration of 160 μg l⁻¹. Moreover, the results demonstrated that the switch was also dependent on the initial total phosphorus concentration. These results suggest that the reservoir in a clear water state is at risk of a switch as nutrient levels are close to the critical levels.     

Alien aquatic vascular plants in Hungary (Pannonian ecoregion): Historical aspects,data set and trends

Estimating the extent of biological invasions is critical in predicting the effect of exotic species. We investigated the occurrence and number of alien freshwater plants and give information on the composition of alien aquatic flora, their trend in time, invasion pathway, and their invasive character.     

Landscape-level seagrass–sediment relations in a coastal lagoon

We investigated the relationships between sediment (subaqueous soil) properties and eelgrass (Zostera marina L.) distribution to develop landscape-level soil-based strategies for choosing eelgrass restoration locations. Subaqueous soils were sampled and eelgrass cover determined for 14 soil-landscape units within a 116 ha area of Ninigret Pond, a coastal lagoon in Rhode Island, USA. Of the 14 soil-landscape units sampled for eelgrass cover, 52% had virtually no eelgrass cover (<10%), while 18% had high eelgrass cover (>90%). The Lagoon Bottom, Shallow Lagoon Bottom, Flood-tidal Delta Slope, and Barrier Cove subaqueous soil-landscape units had the highest eelgrass cover (66–100%). A weak relationship between eelgrass cover and water depths (r² = 0.10) was observed suggesting that properties other than water depth may also control eelgrass distribution. Subaqueous soils on landscapes with >60% eelgrass cover had relatively high levels of acid-volatile sulfides (>90 μg/g), high soil salinity levels (34–44 ppt), fine textures (silt loam), and relatively high total nitrogen levels (>0.15%). Four principal components accounted for 81% of the variability in eelgrass cover. The first component reflected particle-size distribution (i.e. sand, silt, and clay contents) effects and accounted for 43% of the variability. The other components suggested that eelgrass cover is correlated to carbonaceous remains, non-calcareous rock fragments and soil salinity. These data suggest that the current distribution of eelgrass within the study area is strongly influenced by physical and chemical subaqueous soil characteristics. Soil survey techniques proved useful for the delineation of sediment characteristics (e.g. texture, salinity) that influence eelgrass distribution patterns at landscape-level scales.     

沉水植物光合作用的特点与研究进展

沉水植物属于高等植物,由陆生被子植物演化而来,它们在形态、光合生态生理方面对水下生活环境发生了一系列适应性变化。沉水植物的光合作用受水体中光、温度、pH和无机碳等影响,本文对此进行了综述。水中低CO2扩散率以及细胞外较厚的扩散层阻碍了沉水植物净碳的吸收,因此,沉水植物光合作用速率受到无机碳供应的限制。为获得无机碳,沉水植物在形态结构和生理生化上表现一定的特性,包括薄的叶片层并含有叶绿体以及对HCO3-利用的能力,拟C4型和CAM型光合代谢途径的选择。这些是沉水植物碳浓缩机制的具体体现。     

灵芝转化苦参水提物的3个新生成分体外抗乙型肝炎病毒作用

先在基础培养基中添加苦参水煎汁,然后培养灵芝,得到灵芝培养液,再按乙醇氯仿-5%碳酸氢钠溶液-氯仿的顺序提取培养液中的有机酸成分,用制备高效液相色谱分离,得到6个新组分,用这些组分分别作用于转染了乙型肝炎病毒DNA的2.2.15细胞,用固相放射免疫法测定细胞培养上清液中的乙肝病毒表面抗原(HBsAg)和e抗原(HBeAg)的含量,用四甲基偶氮唑盐(MTT)法测定细胞的存活率。结果表明,其中的3个组分对2.2.15细胞分泌HBsAg和HBeAg有抑制作用,提示可能具有抗乙肝病毒的作用。     

Changes in the allocation of some chemical compounds in structures of Oryza glumaepatula (Steud) in an Amazonian lake subjected to an anthropic impact (Lake Batata, Porto Trombetas)

Lake Batata is a typical clear water lake of the Amazon, located at the right margin of the Trombetas River, at the town of Porto Trombetas (PA). It is subjected to a large and predictable variation of the water level, greater than 6 m, being in the floodplain of the Trombetas River. For 10 years (1979–1989) Lake Batata has received the tailings of bauxite processing from the activities of Mineração Rio do Norte S.A. These tailings impacted about 30% of its total area with an effluent of fine granulometry. Nowadays, two different areas can be observed at Lake Batata, one impacted by the bauxite tailings and one where the natural characteristics have been preserved. The aquatic macrophyte Oryza glumaepatula (Steud), known as wild rice, is one of the species found in the two areas, impacted and natural. The goal of this research was to evaluate the concentration of organic matter, organic carbon, N, P, lipids, soluble carbohydrates, and cell-wall fraction in three structures of O. glumaepatula (leaves and culm, adventitious roots, and basal roots), as well as to identify the possible differences in the allocation of these compounds between individuals in the natural and impacted areas. While the differences between the different structures of the plant are preliminary data for studies on the detritus chain and herbivory, the differences between the natural and impacted areas show the probable impact of the tailings on O. glumaepatula.