Zuoxing Zheng

DECOLORIZATION OF POLYMERIC DYES BY A NOVEL PENICILLIUM ISOLATE

Abstract A novel polymeric dye-degrading fungal strain ATCC 74414 was isolated. Taxonomic identification including morphological and cultural characterization indicated that this isolate was a strain of Penicillium. Strain ATCC 74414 aerobically decolorized both Poly R-478 and Poly S-119 in liquid media containing 0.01% of polymeric dyes. The decolorization rate was examined in three distinct liquid media: Schenk and Hildebrandt-K2SO4 medium (SHK), potato dextrose broth (PDB), and half Murashige-Skoog medium (HMS). Strain ATCC 74414 rapidly decolorized R-478 in SHK medium but the color was subsequently released from the mycelial mass into the medium after 2–3 days, indicating that the decolorization in SHK medium could be due to adsorption of Poly R-478 by the mycelia. In contrast, in HMS and PDB media ATCC 74414 decolorized Poly R-478 more steadily, and the dye was initially adsorbed onto the mycelia and was subsequently decolorized without being released into the medium. Strain ATCC 74414 also decolorized Poly S-119 steadily in SHK, HMS and PDB media. It appears that the decolorization process involved initial mycelial adsorption of dye compounds, which was probably followed by biodegradation through microbial metabolism, and the decolorization may be affected by medium constituents. Although aerobic decolorization may not necessarily lead to complete mineralization of dyes, these results have suggested the potential of strain ATCC 74414 in bioremediation of dye-contaminated water and soil.

Solid state production of polygalacturonase by Lentinus edodes using fruit processing wastes

Fruit-processing wastes including apple pomace, cranberry pomace and strawberry pomace were used as substrates for polygalacturonase (PG) production by Lentinus edodes through solid-state fermentation. Strawberry pomace was the best substrate for highest PG yield, followed by apple pomace, while cranberry pomace was not a suitable substrate for PG production in this study. The highest PG activity was obtained after 40 days of culture and the yields from strawberry pomace, apple pomace and cranberry pomace were 29.4 U, 20.1 U and 14.0 U per gram of pomace, respectively. PG activity was increased by the addition of polygalacturonic acid in the apple pomace and cranberry pomace media, but was not affected in strawberry pomace medium. The PG produced by L. edodes from strawberry pomace exhibited a maximal activity at 50°C and at pH 5. The enzyme was fairly stable up to 50°C and between pH 3.0 and 6.5. The acid tolerant property of the enzyme made it suitable for applications in most fruit and vegetable processing industries. This value-added bioconversion strategy may be applicable for the utilization of other food processing wastes.

A model for enhanced pea seedling vigour following low pH and salicylic acid treatments

Abstract In the simplest of terms, seed vigour is a visual measure of a seed’s ability to germinate and survive its early growth and development period. Improvement of seed vigour is important for optimal emergence, stress resistance and uniform growth of emerging seedlings. We have hypothesized that acid-induced cell growth and elongation is regulated through the pentose-phosphate pathway; therefore, the effect of acidification linked to salicylic acid (SA) on growth, cell elongation, and phenolic synthesis was investigated. The experiments consisted of low pH and SA treatments followed by the measurement of phenolic levels and assay of the key regulatory enzyme of the pentose-phosphate pathway, glucose-6-phosphate dehydrogenase (G6PDH), and guaiacol peroxidase (GPX), during post-germination growth and elongation of peas. Phenolic and enzyme levels were determined by UV spectrophotometric assays. A low pH environment stimulated phenolic synthesis and increased tissue rigidity. Stimulating phenolic synthesis through low pH treatment supports the hypothesis that acid-induced cell growth and elongation may be regulated through the pentose-phosphate pathway. Based on concomitant stimulation of G6PDH and increase in proline content, the pentose-phosphate pathway may be linked to stimulation of proline metabolism in response to the above treatments. It has been hypothesized that this pathway produces the critical precursors for the synthesis of phenolic secondary metabolites that are important for plant growth and lignification.

Cranberry processing waste for solid state fungal inoculant production

Abstract Cranberry pomace is a primary by-product of the traditional cranberry juice processing industry and its disposal presents economic and environmental problems. Microbial conversion of cranberry pomace into various value-added products is a practical approach for solving such disposal problems. The present research was undertaken to test the growth of several agriculturally and industrially important fungi on cranberry pomace substrate through solid-state fermentation. Fungi, such as Trichoderma viride If-26, Trichoderma harzianum ATCC 24274, and Trichoderma pseudokoningii ATCC 26801, a novel polymeric dye decolorizing Penicillium isolate, and a food-grade Rhizopus strain isolated from Tempeh, that produce industrially important extracellular enzymes were grown on a cranberry pomace-based medium at 25°C for 4 days. The glucosamine content of the heterogeneous fermented mixture was a good indicator of fungal growth. The maximum growth of all fungi was established on cranberry pomace supplemented with 0·05 g of CaCO 3 , 2·0 ml of water, and 0·05 g of NH 4 NO 3 or 0·2 ml of fish protein hydrolysate per gram of pomace. It was concluded that bioconversion of cranberry processing waste by industrially beneficial fungi through solid-state fermentation was feasible. This potential can be coupled with the utilization of fish processing waste as an organic nitrogen source to develop mutually complementary products benefiting both the fishery and cranberry processing industries.

A mathematical model for the growth kinetics and synthesis of phenolics in oregano (Origanum vulgare) shoot cultures inoculated with Pseudomonas species

Abstract Elicitation with Pseudomonas sp. reduced hyperhydricity in clonally propagated shoot cultures of oregano under in vitro conditions and over many subcultures without re-inoculation. This was characterized by changes in the growth kinetics, total chlorophyll, total phenolics and moisture content. Total chlorophyll in the inoculant-containing shoot cultures was higher than the control throughout the growth cycle of all subcultures. Moisture content (wb) of the inoculated shoot cultures was 8% lower than the control. The pattern of total phenolics synthesis in the inoculated shoot cultures showing characteristics of a periodic response and significant differences when compared to control was observed. A Leudking-Piret’s logistic model was used to study the growth kinetics of the control and inoculated shoot cultures to describe quantitatively the differences in the growth kinetics. There was a fourfold reduction in the biomass by fresh weight and a twofold reduction by dry weight due to inoculation. The specific growth rate remained unchanged, but the length of the growth cycle was reduced by 6 days for the inoculated shoot cultures. It appeared that the growth reduction was linked to the stress-related response mediated by the elicitation from Pseudomonas sp. to stimulate the synthesis of secondary metabolites. In spite of the growth reduction, the inoculated shoot cultures, however, had similar numbers of shoot node explants for subsequent propagation and all the shoot node explants were unhyperhydrated.

Enhancement of pea (Pisum sativum) seedling vigour and associated phenolic content by extracts of apple pomace fermented with Trichoderma spp.

Abstract We previously reported that three apple pomace-based Trichoderma inoculants enhanced seedling vigour in pea ( Pisum sativum ) germinated in potting soil. The objective of this study was to further investigate the effect of isolated extracts from these bioinoculants on phenolic content and seedling vigour in peas. When pea seeds were pre-treated with Trichoderma viride , Trichoderma harzianum and Trichoderma pseudokoningii inoculant extracts, the germination rate in potting soil increased by, 15, 15 and 20%, respectively, compared with water treatment control. After 5 days of growth, the average plant height increased by 27, 39 and 31%, respectively; the average fresh weight increased by 33, 46 and 36%, respectively. The average phenolic content, another key indicator of vigour identified in our studies, increased by 13, 18 and 17%, respectively. The root elongation during germination of pre-treated pea seeds was more rapid than control. Pea seeds treated for 24 h with the dilution of 10 −2 of Trichoderma inoculant extracts resulted in the most rapid plant growth and highest phenolic content of pea seedlings. The chemical composition of the inoculant extracts was partially characterized.

A model for the role of the proline-linked pentose phosphate pathway in polymeric dye tolerance in oregano

Abstract Polymeric dyes are aromatic hydrocarbon compounds that are similar to aromatic soil pollutants and inhibit plant growth. Polymeric dye-tolerant plants may be useful in phytoremediation because they could provide a rhizosphere suitable for colonization by microbes that are efficient degraders of aromatic compounds. Plants that produce high levels of phenolic compounds may be more tolerant of aromatic contaminants because of their inherent mechanisms for degrading or sequestering endogenous aromatic compounds. A clonal line of oregano ( Origanum vulgare ) O-1 that is highly tolerant of the polymeric dye R-478 has been isolated. Over a time course of exposure to 0.1% Poly R-478, O-1 plants showed a progressive decrease in total phenolic compounds, whereas peroxidase activity and free proline levels increased. The inverse relationship between phenolics and peroxidase activity suggests a role for peroxidase-mediated lignification in polymeric dye tolerance. The increased level of free proline in response to polymeric dye exposure suggests that phenolic synthesis requires proline synthesis and/or oxidation. These results support our working model that aromatic pollutant-tolerance may be regulated through the proline-linked pentose phosphate pathway, a primary metabolic pathway.

Effect of apple pomace-based Trichoderma inoculants on seedling vigour in pea (Pisum sativum) germinated in potting soil

Abstract Three Trichoderma inoculants were produced by growing T. viride , T. harzianum and T. pseudokoningii on apple pomace-based medium at 20°C for 7 days. The Trichoderma inoculants were mixed with potting soil at a ratio of 1:5 (v/v) and the mixture was used for germination tests of pea ( Pisum sativum ) seeds. When T. viride , T. harzianum and T. pseudokoningii inoculants were applied to the soil, the germination rate of pea seeds increased by 20, 40 and 15%, respectively, compared to the potting soil control. After 5 days the average plant height increased by 52, 67 and 48%, respectively, while the average fresh weight of seedlings increased by 26, 63 and 25%, respectively. The average total phenolic content of pea seedlings increased by 14, 18, and 12% respectively. Among those three Trichoderma inoculants, however, only T. harzianum inoculant increased plant height and fresh weight significantly, while both T. harzianum and T. viride inoculants increased phenolic content of seedlings significantly. The apple pomace control increased the germination rate, plant height and fresh weight slightly, but did not increase the phenolic content of pea seedlings. These results suggest that Trichoderma species grown on apple pomace-based medium can enhance seed performance of peas according to some criteria of seedling vigour and thus have potential for use as seed treatment.