Lignocellulolytic mutants of Pleurotus ostreatus induced by gamma-ray radiation and their genetic similarities

Creating a novel genetic diversity of Trichoderma afroharzianum by γ-radiation for xylanase-cellulase production

Creating novel sources of a microbial strain using induced mutation can increase enzyme production for industrial use. According to this, we have developed a mutant strain of Trichoderma afroharzianum by Co60 gamma irradiation. Trichoderma mutants were isolated from an optimum dose of 250 Gy. The qualitative and quantitative screening were used for evaluating their enzyme production and the DNA barcoding method was used to identify the best Trichoderma mutant isolates. The highest cellulase (exo-glucanase, endoglucanase, β-glucosidase, and total cellulase) and xylanase activities were observed in superior mutant isolates of Trichoderma afroharzianum NAS107-M44 and Trichoderma afroharzianum NAS107-M82, which is approximately 1.6-2.5 times higher than its parent strain, respectively. The electrophoretic pattern of proteins showed that the exo-glucanase I, endo-glucanase III, and the xylanase I enzymes hydrolyzed the corn bran, synergistically. Overall, gamma irradiation-induced mutation could be an expedient technique to access such superior mutants for the bioconversion of corn bran wastes.

Induced mutation in Agaricus bisporus by gamma ray to improve genetic variability, degradation enzyme activity, and yield

PURPOSE

Genetic variability in white button mushroom cultivars is very low due to the life cycle. Induction mutations using gamma irradiation is a useful way to generate diversity in white button mushrooms to obtain genotype(s) with desirable traits.

METHODS

Gamma irradiation Cobalt-60 was used for inducting genetic diversity in white button mushroom to obtain genotype(s) with desirable traits. Gamma irradiation with doses of 0-500 Gy was conducted on spores on Potato Dextrose Agar medium.

RESULTS

The results showed significant differences in days to pin production and harvest, fruit body number, fresh and dry weight, yield, laccase, and manganese peroxidase enzyme activity. After isolating variants, 15 variants were selected on the base of their high yield and enzyme degradation activity. Their genetic variation was confirmed by Sequence Related Amplified Polymorphism (SRAP) markers, and then incubated on three types of substrates (50:50, 75:25, and 100:0 % compost: raw straw). The results showed that all variants, except GR18, colonized in 75:25, and GR3, GR4, GR9, GR61, GR72, and GR74 variants colonized in 50:50. In 100:0 substrate, GR55 and GR63 were the earliest variants, and GR9 produced the highest fruit body number. In 75:25 substrate, GR9, GR3, GR61, GR4, GR74, GR4, GR61, and GR72 showed higher yields. The highest laccase and manganese peroxidase activity were recorded in GR3, GR4, GR9, GR72, and GR61. The isolated 15 variants were clustered into two main groups by cluster analysis and genetic variation was confirmed by SRAP markers.

CONCLUSION

The results showed that the diversity in the white button mushroom could be improved using gamma rays, and the variation would be useful for the development of future breeding programs.

Development of improved strain in species of Pleurotus by gamma irradiation

The oyster mushroom (Pleurotus spp.) is the second important edible mushroom in the world, with 19 per cent contribution to total mushroom production (Sharma et al., Mushroom Res 26(2):111-120, 2017). The cultivated mushrooms face the problems like loss of genetic diversity and strain degeneration (Wang et al., Curr Microbiol 65(4):424-431, 2012). Thus to enhance the productivity within short duration, three species of Pleurotus namely Pleurotus djamor, Pleurotus florida and Pleurotus ostreatus were gamma irradiated at 20 and 25 Gy at 9.779 kGy/h and performance of mutants followed by three generation of selection in paddy straw substrate were observed. Biological efficiency (BE) of P. djamor mutants irradiated at 20 Gy was increased by 9.25 per cent. The number of days taken for primordial initiation was also reduced by 1 day compared to P. djamor. P. florida irradiated at 25 Gy recorded increase in sporocarp size over P. florida. The biological efficiency of P. ostreatus irradiated at 25 Gy was improved by 12.89 per cent and there was earliness in primordial initiation by 3 days compared to P. ostreatus. The polymorphism per cent was analysed by Random Amplified Polymorphic DNA (RAPD) and revealed that P. djamor, P. florida and P. ostreatus had 16.70%, 25% and 22% polymorphism with their respective improved strains.

Anthraquinone dyes decolorization capacity of anamorphic Bjerkandera adusta CCBAS 930 strain and its HRP-like negative mutants

Cultures of the anamorphic fungus Bjerkandera adusta CCBAS 930 decolorizing, in stationary cultures, 0.01 % solutions of carminic acid and Poly R-478, were characterised by a strong increase in the activity of the horseradish peroxidase (HRP-like) and manganese-dependent peroxidase (MnP) at a low activity of lignin peroxidase. Genotypically modified mutants of B. adusta CCBAS 930: 930-5 and 930-14, with total or partial loss of decolorization capabilities relative to anthraquinonic dyes, showed inhibition of the activity of HRP-like peroxidase and MnP. Whereas, compared to the parental strain, in the mutant cultures there was an increase in the activity of lignin peroxidase and laccase. The paper presents a discussion of the role of the studied enzymatic activities in the process of decolorization of anthraquinonic dyes by the strain B. adusta CCBAS 930.

Selection of TcII Trypanosoma cruzi population following macrophage infection

BACKGROUND

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, which exhibits a high genetic variability. TcI, TcII, or mixed TcI/TcII strains may be found during acute human infection while mainly TcII parasites are present at the chronic stage of disease. In a previously studied Chagas disease outbreak, we identified mixed TcI/TcII strains in the vector Triatoma tibiamaculata and only TcII strains in infected humans, indicating that T. cruzi populations may be selected within the human host.

METHODS

Utilizing molecular typing and cell biology techniques, we investigated the interaction of TcI, TcII, and mixed TcI/TcII strains with macrophages, an important cell population implicated in controlling protozoan infection.

RESULTS

TcII but not TcI strains were selected by both human and murine macrophages in vitro and by peritoneal cavity cells in vivo. Biological analysis revealed that, compared with TcI, TcII strains display higher infective and multiplicative ability as well as lower doubling time inside macrophages. However, TcI and TcII strains present similar susceptibility to interferon-γ-activated macrophages in vitro.

CONCLUSIONS

Taken together, our results reveal the existence of an intracellular selection process in macrophages that favors TcII, but not TcI, when infection occurs with vector-derived mixed TcI/TcII strains.

Molecular characterisation of UV and chemically induced mutants of Trichoderma reesei FCBP-364

Cellulases are a highly diverse group of enzymes whose function is crucial to the healthy functioning of the biosphere, since more than half of all biomass on the planet consists of their substrate, cellulose. Trials were conducted to study the effect of mutagenesis by ultraviolet (UV) irradiation (5-40 min) and ethyl methane sulphonate (EMS) treatment (50-300 microg mL(-1)) to obtain hyperactive cellulase enzyme producers. Putative mutants of Trichoderma reesei FCBP-364 were selected on the basis of their bigger hydrolysing zone formation and compared to the parental strains quantitatively. UV- and EMS-treated putative mutants of the test strains exhibited a 1.5-2-fold enhancement in enzymatic activity over the parental strain. The profile of genetic variability among native and mutant derivatives was scrutinised through random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR). The scanned amplicons confirmed the modification in genetic make up which might be the cause of the stir up in the enzyme activity.

Mutagenesis and genetic characterisation of amylolytic Aspergillus niger

Aspergillus niger FCBP-198 was genetically modified for its ability to reveal extra cellular alpha-amylase enzyme activity. From 76 efficient mutants isolated after ultraviolet (UV) irradiation, An-UV-5.6 was selected as the most efficient UV mutant, with 76.41 units mL(-1) of alpha-amylase activity compared to wild (34.45 units mL(-1)). In case of ethyl methane sulphonate (EMS), among 242 survivors, 74 were assayed quantitatively and An-Ch-4.7 was found to be the most competent, as it exhibited a three-fold increase in alpha-amylase activity (89.38 units mL(-1)) than the parental strain. Genetic relationships of the mutants of A. niger FCBP-198 were analysed with a randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Results obtained from the comparison between genotypes of A. niger FCBP-198 showed differences in the sizes and numbers of amplified fragments per primer for each isolate. The dendrogram showed that genotypes An-Ch-4.7 and An-Ch-4.2 were distinctly classified into one category, while the isolates An-UV-5.6, An-UV-5.1 and A. niger FCBP-198 have the nearest genetic relationship. The five isolates from A. niger FCBP-198 genotypes shared an average of 65% bands.

Mutagenesis and Genotypic Characterization of Aspergillus niger FCBP-02 for Improvement in Cellulolytic Potential

Cellulase is a collective term that encompasses enzymes which catalyze reactions that participate in the degradation of insoluble cellulose to soluble carbohydrates. In the present study, production of extra cellular cellulases by a filamentous fungus, Aspergillus niger FCBP-02, was studied in solid-state fermentation (SSF) as well as in submerged fermentation (SmF). Trials were conducted to evaluate the effect of mutagenesis by UV irradiation (5–40 min) and ethyl methane sulfonate (EMS) treatment (50–300 μg mL−1) to obtain hyper active cellulase enzyme producers among the potential strains. The enzyme activity assays of parental and mutant strains clearly revealed significantly higher cellulase activity of mutant A-Ch-5.5 (96 Units mL−1), followed by A-UV-5.6 (71 Units mL−1) with respect to the wild strain of A. niger FCBP–02 (53.7 Units mL−1). The profile of genetic variability among wild and mutant derivatives was scrutinized through RAPD–PCR. The expression pattern of mutants exhibited that the mutants were isogenic variants of the wild type and the out performance of the mutants could be attributed to the change in genetic make up.