Preparation of immobilized Trametes pubescens laccase on a cryogel-type polymeric carrier and application of the biocatalyst to apple juice phenolic compounds oxidation

A new biocatalyst was prepared by the immobilization of a Trametes pubescens laccase, into a wide-pore poly(vinyl alcohol) cryogel. The known enzyme was produced and purified by the previously described procedure. The resulted laccase (yield 40%) has an activity of 46.4 U mg⁻¹ and 12.51 mg mL⁻¹ protein content. The enzyme was subsequently immobilized in a functionalized macroporous cryogel beads by a covalent immobilization technique. The time dependence of the immobilization process and the enzyme loading of the carrier material (5.2 mg g⁻¹ cryogel) were determined by measuring the decrease of protein amount in the enzyme solution. In conversion experiments, a higher stability of the immobilized biocatalyst compared to the free enzyme was evidenced. Steady-state kinetic characterization of four phenols (catechol, caffeic and chlorogenic acids, and catechin) has been performed with free and immobilized laccase, the catalytic parameters being determined and compared. The effect of both laccases (free and immobilized) on the phenol content of retailed apple juice samples, having the same initial composition, was also investigated by working in batch conversion. The variation in phenolic compound content has been compared with that of an untreated apple juice sample having initially the same content of phenolic compounds. A number of advantages resulted in using the immobilized laccase for the apple juice treatment (conservation to some extent of enzyme activity, higher content of phenols preserved, easy separation of the enzyme from the apple juice, therefore avoiding the possible unhealthy effects due to the remaining protein, etc.).     

Lipid oxidative changes in chitosan-oregano coated traditional dry fermented sausage Petrovská klobása

The effect of a chitosan coating with added essential oil of oregano (Origanum vulgare) on lipid oxidation of dry fermented sausage (Petrovská klobása) was investigated. Fatty acid profile, aldehyde contents and sensory analysis of odor and flavor were determined after drying and during seven months of storage.     

"环保酒精"——粮食转化酒精及饲料产品的综合技术

俄罗斯有150多家酒精工厂,工厂平均年产量1万t左右,主要原料为大麦、小麦、玉米和黑麦等。俄罗斯食品生物技术科学研究所是俄罗斯研究酒精生产、酶制剂和酵母的权威机构,该所开发的酒精生产工艺在世界上处于领先地位。其主要技术成果包括:65～80℃低温蒸煮,双酶法糖化,28～38℃中高温快速浓醪发酵,蒸馏废水回用等项技术;其中机械涡流均质是一项有效的节能技术,可节约能耗20%左右。     

Antioxidant and cell growth activities of beet root pomace extracts

Beetroot (Beta vulgaris) pomace, processing by-product from food industry, was investigated in this work as a starting raw material. The contents of phenolics (1.87–11.98 mg GAE/g of dry weight) and betalains (0.75–3.75 mg betalains/g of dry weight) in the extracts were determinated spectrophotometrically. Some individual phenolic compounds, including ferulic, vanillic, p-hydroxybenzoic, caffeic and protocatehuic acids, were identified and quantified by HPLC. The antioxidative activity of beetroot extracts was tested using DPPH, hydroxyl and superoxide anion radicals by ESR spectroscopy. ${\text{IC}}_{50}^{{}^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}}\text{OH}}$ (0.05–0.108 mg/ml), $\text{IC}{50}^{{\text{DPPH}}^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}}}$ (0.183–0.333 mg/ml), and ${\text{IC}}_{50}^{{\text{O}}_2^{\text{<mglyph src="https://sdfestaticassets-us-east-1.sciencedirectassets.com/shared-assets/16/entities/rad"></mglyph>}-}}$ (0.198–1.000 mg/ml) were calculated. The regression analysis produced moderate to high correlation coefficients between the scavenging activities and phenolics, and some individual phenolic compounds which indicated that beetroot pomace may be used as functional food ingredient. Cell growth effects were determined in MCF7 and MRC-5 cell lines, using SRB assay. IC₅₀ values were in the range of 362.478–503.525 and 383–587.880 μg/ml in MRC-5 and MCF7, respectively.     

Using lactic acid bacteria for developing novel fish food products

Lactic acid bacteria‐induced fermentation of fish was tested with the purpose of developing a novel fish food product with desired meat properties. Three selected lactic acid bacteria strains, isolated from lightly preserved fish products, were inoculated into minced frozen fillet of yellowfin tuna, and changes in fish properties were observed during 52 days of storage at 8 °C. Organoleptic, bacteriological and biochemical studies (pH, histamine, TVB‐N, malonaldehyde) and shelf‐life measurements suggest that Leuconostoc mesenteroides could be considered as a possible starter culture for fish fermentation, but additional experiments should be performed. © 2000 Society of Chemical Industry     

Analysis of global approaches to the simulation of counter-current separators

The status of research and development of simulation of counter-current separation processes via global approach is discussed. A general numerical method for calculation of separation equipment should be able to handle easily various modifications in configuration. Global solution of all governing equation results in a procedure which is flexible enough to perform all types of calculations. Classification of difficult separation problems indicates which one should be solved by a global approach. A general strategy of calculation of multicomponent counter-current separation processes via a global approach is presented.     

Alcohol oxidase- and formaldehyde dehydrogenase-based enzymatic methods for formaldehyde assay in fish food products

For Gadoid fishes, formaldehyde can be generated in tissues in huge amounts during endogenous enzymatic degradation of natural osmoprotectant trimethylamine-N-oxide. This paper describes two enzymatic methods for assay of formaldehyde in fish food products using alcohol oxidase (AOX) and formaldehyde dehydrogenase (FdDH) isolated from the thermotolerant methylotrophic yeast Hansenula polymorpha. AOX-based method exploits an ability of the enzyme to oxidise a hydrated form of formaldehyde to formic acid and hydrogen peroxide monitored in peroxidase-catalysed colorimetric reaction. In FdDH-based method, a monitored coloured formazane is formed from nitrotetrazolium salt during reduction by NADH, produced in formaldehyde-dependent reaction. It was demonstrated an applicability of both methods for assay of formaldehyde in fish products. The optimal protocols for analysis procedures have been elaborated and analytical parameters of both enzymatic methods have been established. The both methods were demonstrated that some fish products (hake and cod) contain high formaldehyde concentrations (up to 100 mg/kg wet weight).     

天然与合成紫晶的3 543 cm-1红外吸收谱带及其鉴定价值

重点对3 800～3 000 cm-1范围的红外吸收光谱在鉴别天然与合成紫晶中的适用性和局限性进行了研究.3 680, 3 664, 3 630 cm-1处吸收带的存在可以确认紫晶为人工合成的, 但仅指那些在近中性NH4F溶液中合成的紫晶.相反, 商业上大量的合成紫晶是在碱性K2CO3溶液中合成的, 这些紫晶的红外吸收光谱并无明显的鉴定特征.前人的研究发现了在近3 595, 3 543 cm-1处吸收带的潜在鉴定价值.3 595 cm-1吸收带在合成紫晶的红外吸收光谱中并未出现, 在一些天然紫晶中也常常缺失.3 543 cm-1吸收带出现在绝大多数碱性溶液中合成紫晶的红外吸收光谱中, 但有时也在天然紫晶中出现.因此, 它只是鉴别合成紫晶的临时性证据.3 543 cm-1吸收带在有些类型的合成紫晶中缺失.要准确地鉴定天然与合成紫晶一定要根据其红外光谱、内部生长结构(包括双晶)和包裹体特征综合判断.