Extractive lactic acid fermentation using ion-exchange resin

Lactic acid fermentation is an end-product-inhibited reaction. The restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques. Studies were performed by attaching an ion-exchange resin packed column with a 2-L fermentor for separation of lactic acid. The fermentation, in a conventional batch mode, resulted in a lactic acid yield of 0.828 g . g(-1) and a lactic acid productivity of 0.313 g . L(-1) . h(-1). However, these could be further enhanced to 0.929 g . g(-1) and 1.665 g . L(-1) . h(-1) by extractive fermentation techniques. The effect of temperature on extractive fermentation was remarkable and has been included in this work.     

Strategies for reducing solvent toxicity in extractive fermentations

The toxicity of an Alamine 336/oleyl-alcohol extraction system on Lactobacillus delbrueckii was investigated. It was shown that the solvent affected the cells through the water-soluble portion and the immiscible portion of the solvent. While immobilization significantly protected the cells from the immiscible solvent phase, the water-soluble part of the solvent still caused toxicity to the microorganisms due to diffusion of the solvent into the matrix. Adding soybean oil to the kappa-carrageenan matrix could trap the diffusing solvent molecules, and therefore reduce the toxic effect from the water soluble portion of the solvent. The protective ability of soybean oil was quantified through mathematical modeling and experimentation.     

Can we rely on forest reserves for primate conservation?

Tropical forests contain much of the world's biodiversity, yet their rate of decline is increasing. The strategy most frequently used to protect this biodiversity is to make parks and reserves. While there is a great deal of research on the effectiveness of parks for protecting biodiversity, there is little research on how well extractive reserves conserve biodiversity. Here, we evaluate the effectiveness of four forest reserves in western Uganda at maintaining populations of primates and compare census data from the reserves to data from the neighbouring well‐protected Kibale National Park. The relative abundance of the five most common primates in the park was approximately four times that of the forest reserves. In the forest reserves, evidence of new human encroachment was seen every 500 m, while in the park it was seen every 100,000 m. Two recommendations emerge from our research: (i) for forest reserves, such as those studied here, to have conservation value for primates, extraction must be reduced and (ii) until the long‐term viability of the populations in forest reserves can be ascertained, they should not be considered in estimates of the sizes of endangered species protected ranges.     

Biotechnology of Microbial Xylanases: Enzymology,Molecular Biology,and Application

ABSTRACT:?

Xylanases are hydrolases depolymerizing the plant cell wall component xylan, the second most abundant polysaccharide. The molecular structure and hydrolytic pattern of xylanases have been reported extensively and the mechanism of hydrolysis has also been proposed. There are several models for the gene regulation of which this article could add to the wealth of knowledge. Future work on the application of these enzymes in the paper and pulp, food industry, in environmental science, that is, bio-fueling, effluent treatment, and agro-waste treatment, etc. require a complete understanding of the functional and genetic significance of the xylanases. However, the thrust area has been identified as the paper and pulp industry. The major problem in the field of paper bleaching is the removal of lignin and its derivatives, which are linked to cellulose and xylan. Xylanases are more suitable in the paper and pulp industry than lignin-degrading systems.     

Ecological total-factor energy efficiency of China’s energy intensive industries

This paper uses a meta-frontier slack-based DEA model to measure the ecological total-factor energy efficiency as well as the energy conservation potential of China’s four energy intensive subsectors. We incorporate both desirable and undesirable output together in the period, 2000–2013. The conclusions are: firstly, under the meta-frontier, the four subsectors of energy intensive industries have low average level of ecological total-factor energy efficiencies. They are 0.137, 0.212, 0.238, and 0.307 in the non-metallic mineral products manufacturing industry, raw chemical materials and chemical products manufacturing industry, smelting and pressing of ferrous metals industry, and smelting and pressing of non-ferrous metals industry, respectively. Secondly, the ecological energy efficiency in East China is the highest among three regions. Central China and West China are behind, but they are extremely close to each other. Thirdly, East China almost has no technology gap pertaining to energy efficiency, while Central China and West China almost have the same gap. Finally, Sichuan is considered to be the best province in West China under group frontier due to its perform in the three energy intensive subsectors. For Central and East China, no province has higher ecological energy efficiency in more than two energy intensive subsectors.     

生物柴油耦联丙酮丁醇发酵的初步研究

以4种生物柴油(原料为地沟油、菜籽油、棕榈油和废肯德基油)作为萃取剂,开展了丙酮丁醇静态萃取发酵。通过分析发酵过程中的产气量及发酵40 h后油水两相中的溶剂浓度,发现生物柴油对丙丁梭菌有毒性。另外,静置条件下丁醇在不同油水两相中的液液平衡系数大致相同。在发酵24 h时加入棕榈生物柴油(油水体积比为0.4∶1),丁醇发酵强度达到最大值0.213 g.(L.h)-1、比对照(传统发酵)提高10.9%,且生物柴油中的丁醇质量浓度达到6.44 g.L-1。     

Enhancement of 2-phenylethanol productivity by Saccharomyces cerevisiae in two-phase fed-batch fermentations using solvent immobilization

The bioconversion of L-phenylalanine to 2-phenylethanol by Saccharomyces cerevisiae in fed-batch experiments has shown that concentrations of 2-phenylethanol of >2.9 g/L have a negative impact on the oxidative capacity of the yeast. Without tight control on ethanol production, and hence on the feed rate, ethanol rapidly accumulates in the culture media, resulting in complete inhibition of cell growth before the maximal 2-phenylethanol concentration of 3.8 g/L, obtained in the absence of ethanol production, could be achieved. This effect was attributed to a cumulative effect of ethanol and 2-phenylethanol, which reduced the tolerance of the cells for these two products. To enhance the productivity of the bioconversion, a novel in situ product recovery strategy, based on the entrapment of an organic solvent (dibutylsebacate) into a polymeric matrix of polyethylene to form a highly absorbent and chemically and mechanically stable composite resin, was developed. Immobilization of the organic solvent successfully prevented phase toxicity of the solvent and allowed for an efficient removal of 2-phenylethanol from the bioreactor without the need for prior cell separation. The use of the composite resin increased the volumetric productivity of 2-phenylethanol by a factor 2 and significantly facilitated downstream processing, because no stable emulsion was formed. The 2-phenylethanol could be backextracted from the composite resin, yielding a concentrated and almost cell-free solution. In comparison to two-phase extractive fermentations with cells immobilized in alginate-reinforced chitosan beads, the use of a composite resin was extremely inexpensive and simple. In addition, the composite resin was found to be insensitive to abrasion and chemically stable, such that sterilization with 2 M NaOH or heat was possible. Finally, the composite resin could be produced on a large scale using commercially available equipment.     

Decolorization of textile indigo dye by ligninolytic fungi

The indigo dye is extensively used by textile industries and is considered a recalcitrant substance, which causes environmental concern. Chemical products used on textile processing, which affect the environment through effluents, can be voluminous, colored and varied. Vat textile dyes, like indigo, are often used and dye mainly cellulosic fibers of cotton. Decolorization of this dye in liquid medium was tested with ligninolytic basidiomycete fungi from Brazil. Decolorization started in a few hours and after 4 days the removal of dye by Phellinus gilvus culture was in 100%, by Pleurotus sajor-caju 94%, by Pycnoporus sanguineus 91% and by Phanerochaete chrysosporium 75%. No color decrease was observed in a sterile control. Thin layer chromatography of fungi culture extracts revealed only one unknown metabolite of Rf=0.60, as a result of dye degradation.     

Extractive cultivation of Lactococcus lactis using a polyethylene glycol/MgSO4 · 7H2O aqueous two-phase system to produce nisin

To relieve lactic acid inhibition, an aqueous two-phase system (ATPS) was used to grow Lactococcus lactis. Its composition was 11% (w/v) PEG 20000/3.5% (w/v) MgSO₄ 7H₂O. In this ATPS medium, the cells were completely partitioned in the bottom phase, and lactic acid had the biggest partition coefficient of the eight ATPS media tested. The cell biomass in this medium was 0.64 mg ml^–1, only 60% of that of the control medium, but nisin production (803 IU ml^–1) was enhanced by 33%. The increase in nisin was explained as a result of extraction of lactic acid from the bottom phase to the top one. The changes of tie-line length and phase volume ratio for the identical tie line could affect cell growth and nisin accumulation.