Effects of high‐pressure processing on fungi spores: Factors affecting spore germination and inactivation and impact on ultrastructure

Food contamination with heat‐resistant fungi (HRF), and their spores, is a major issue among fruit processors, being frequently found in fruit juices and concentrates, among other products, leading to considerable economic losses and food safety issues. Several strategies were developed to minimize the contamination with HRF, with improvements from harvesting to the final product, including sanitizers and new processing techniques. Considering consumers’ demands for minimally processed, fresh‐like food products, nonthermal food‐processing technologies, such as high‐pressure processing (HPP), among others, are emerging as alternatives to the conventional thermal processing techniques. As no heat is applied to foods, vitamins, proteins, aromas, and taste are better kept when compared to thermal processes. Nevertheless, HPP is only able to destroy pathogenic and spoilage vegetative microorganisms to levels of pertinence for food safety, while bacterial spores remain. Regarding HRF spores (both ascospores and conidiospores), these seem to be more pressure‐sensible than bacterial spores, despite a few cases, such as the ascospores of Byssochlamys spp., Neosartorya spp., and Talaromyces spp. that are resistant to high pressures and high temperatures, requiring the combination of both variables to be inactivated. This review aims to cover the literature available concerning the effects of HPP at room‐like temperatures, and its combination with high temperatures, and high‐pressure cycling, to inactivate fungi spores, including the main factors affecting spores’ resistance to high‐pressure, such as pH, water activity, nutritional composition of the food matrix and ascospore age, as well as the changes in the spore ultrastructure, and the parameters to consider regarding their inactivation by HPP.     

利用质谱分析法从酶谱鉴定嗜热真菌木聚糖酶

通过对前期筛选到的一株嗜热真菌Talaromyces thermophilus WYN9进行产木聚糖酶的诱导和非诱导培养。诱导培养的上清液中可以检测到木聚糖酶酶活。在非变性胶和变性胶SDS-PAGE中,诱导和非诱导的酶谱条带差异明显。以非诱导酶谱为对照,将诱导酶谱中与其有显著差异的条带切下,回收蛋白,测定酶活。将有木聚糖酶酶活的蛋白通过SDS-PAGE进一步分离纯化,切胶后使用胶内酶切法进行预处理,使用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）进行分析。结果表明该蛋白与拟青霉属Paecilomyces sp. J18的内切木聚糖酶高度同源。根据质谱分析结果设计兼并引物,通过交错式热不对称PCR（thermal asymmetric interlaced PCR,TAIL-PCR）扩增,获得了TtXynA基因全长。根据Kimura双参数模型用临近相邻法构建了TtXynA及其同源蛋白的进化树。     

浓缩果汁中耐热霉菌的分析及鉴定

目的：检测15 个批次浓缩果汁中的耐热霉菌并对其进行鉴定。方法：80 ℃、30 min热处理后涂布平板菌落计数法分离和计数浓缩果汁中的耐热霉菌,分离纯化后观察其显微形态和菌落形态,再采用28S rDNA序列分析鉴定霉菌的种属。结果：这15 批次浓缩果汁中有8 个样品检出耐热霉菌,检出率达53.3%;检出的耐热霉菌以正青霉（Eupenicillium）和篮状菌（Talaromyces）为主,还有少量白耙齿菌、栓菌和座囊菌属。结论：进口或国产浓缩果汁都存在耐热霉菌污染,其中尤其值得注意的是检出了既耐热又能产生真菌毒素的正青霉和篮状菌。     

柄蓝状菌原生质体的制备与再生条件优化

为了建立以聚乙二醇/氯化钙（PEG/CaCl2）原生质体介导的柄蓝状菌（Talaromyces Stipitatus）高效的遗传转化系统,分别从材料选择,真菌菌龄,不同的渗透压稳定剂,酶的不同种类配比,酶的浓度,酶解时间及不同再生方式对柄蓝状菌EMM原生质的制备与再生条件进行优化。结果表明:以柄蓝状菌EMM 接种生长48 h的菌丝为制备材料,1 mol/L MgSO4作为渗透压稳定剂,菌丝在温度为30 ℃,浓度为50 mg/mL的裂解酶溶液中酶解3 h,得到的原生质体先用再生培养基孵化培养12 h,然后再与PDA培养基混合铺板,以上组合条件下原生质体的释放量可达8.73×108 /mL,再生率可达17.7％。     

Heat Activation Characteristics of Talaromyces Ascospores

ABSTRACT: Heat activation of ascospores of 4 strains of Talaromyces was investigated. Dormancy of the ascospores was broken by heating in several buffer solutions. When the heating period was extended, emerged colonies increased at elevated temperatures and the number of colony-forming units (CFU) reached the population of the ascospores. A direct linear relationship was observed between the logarithm of CFU and the heating period at each temperature. Activation rates of the test strains were greater at higher temperatures. Activation energy values of the 4 strains, calculated on the basis of heat activation rates, ranged from 3.83 × 10⁴ to 1.39 × 10⁵ J/mol. The influence of medium on activation was studied by heating in different buffer solutions and fruit juices. The pH of buffer solutions had no effect on heat activation rates. However, activation rate was enhanced by heating in fruit juices.     

Characterization of Talaromyces islandicus–mediated silver nanoparticles and evaluation of their antibacterial and anticancer potential

The biosynthesized silver nanoparticles (AgNPs) have been reported to possess several therapeutic applications. Silver is one of the important metals known for its bioactive properties not only as macromolecule but also as nanoparticle (NP). The current research focused on the eco-friendly synthesis of Talaromyces islandicus VSGF1(Lab code) –mediated AgNPs. The aqueous culture filtrate of T. islandicus VSGF1 was used as a reducing agent. The formation of AgNPs was confirmed by observing the color change from colorless to colloidal earthy-colored and a sharp absorption peak of ultraviolet–visible (UV-vis) spectroscopy at 400 nm. Fourier-transform infrared spectroscopy revealed the involvement of various functional groups for the formation and stabilization of AgNPs. The structure, size, and shape of mycosynthesized AgNPs were identified by X-ray diffraction (XRD), scanning electron microscopy, and atomic force microscopy (AFM) analysis. The XRD analysis exhibited crystalline nature of NPs whereas AFM analysis revealed the spherical shape of AgNP with average size range between 13 and 66 nm. The antibacterial activity of AgNPs (50 μg/ml) investigated against gram-positive and gram-negative bacteria revealed maximum zone of inhibition (ZOI) against drug-resistant Enterococcus faecalis MTCC439 (18.66 ± 0.57 mm) and Pseudomonas aeruginosa MTCC96 (16 ± 0 mm) followed by Staphylococcus aureus MTCC96 (15.33 ± 0.57 mm), Bacillus subtilis MTCC441 (14.66 ± 0.57 mm), and Escherichia coli MTCC45 (14.66 ± 0.57 mm). Further, the AgNPs evaluated for antitumor activity against human hepatocellular carcinoma (HepG2) cell line exhibited promising result with half-maximal inhibitory concentration (MIC) value at 38.17 μg/ml concentration through MTT (methylthiazolyl tetrazolium assay) assay. Apparently, this is the first report from T. islandicus to the best of our knowledge.