Rina D. Koyani

Thermostable xylanase production and partial purification by solid-state fermentation using agricultural waste wheat straw.

A locally isolated strain of Trichoderma harzianum was studied for production of xylanase (EC 3.2.1.8) using lignocellulosic substrates for solid-state fermentation. Among the different substrates used, wheat straw produced the highest yields (146 IU/ml). The influence of temperature, pH, moistening agents, moisture level, carbon sources, nitrogen sources, pretreatments and metal ions were evaluated with respect to xylanase production. Highest xylanase production was obtained using wheat straw after 12 days of incubation. Different substrate combination ratios and the effect of particle size were also checked against xylanase production. Maximum xylanase production was observed in a wheat straw/rice straw ratio of 1:1, with a particle size of 0.45–0.5 mm. Media supplementation with xylose as a carbon source in a ratio 1:5 (carbon source/substrate) gave maximum activity (157 IU/ml). Nitrogen supplementations from yeast extract produced xylanase activity of 141 IU/ml. Optimum xylanase production was observed at 30°C and pH 5.0. Xylanase production was enhanced in the presence of Ca2+ and Zn2+ ions. Ammonium sulfate fractionation (20–80% saturation) of partially purified xylanase yielded 76.5% of the enzyme with a 3.53-fold purification. The molecular weight of xylanase was found to be ca. 29,000 Da by SDS–PAGE.

Pattern of delignification in Ailanthus excelsa Roxb. wood by Inonotus hispidus (Bull.: Fr.) Karst.

The pattern of delignification in Ailanthus excelsa Roxb. wood, naturally infected by Inonotus hispidus (Bull.: Fr.) Karst., was studied by light microscopy. Inonotus hispidus produced a typical pattern of soft rot decay even though it is grouped with white rot basidiomycetes. Fungal hyphae colonised all cell types of the secondary xylem but more damage was observed in xylem fibres. In the early stage, infection commenced on the cell wall corners and middle lamellae of the fibre wall without any pronounced effect on the primary and secondary wall layers. Delignification of fibre wall became apparent when all cell types became completely invaded by fungal hyphae. It started from within the lumina towards the middle lamellae, occurring initially in the immediate vicinity of hyphae growing on the luminal surface by forming an erosion trough. At an advanced stage of decay, localised degradation of lignin, cellulose and hemicellulose resulted in the formation of small cavities within the secondary walls (S2) of fibres. These cavities were never observed to contain any fungal hyphae. Though the vessels were resistant to infection, xylem rays and fibres were relatively less resistant to attack by I. hispidus. In severe infection, vessel lumens were found to be filled with sclerotic tissue which blocked them, resulting in complete collapse. The formation of cavities and the extent of cell wall damage are described in detail.

Anatomical changes in the stems of Azadirachta indica (Meliaceae) infected by pathogenic fungi.

Development of gum ducts and chemical nature of occluding material was studied by histological and histochemical methods in the differentiating xylem of Azadirachta indica A.Juss. In response to injury and subsequent fungal infection the stem developed vascular occlusions and gum resin cavities. Fungal hyphae were observed in all the cell types of xylem including vessel elements and associated parenchyma cells. Chemical nature and forms of the occluding material in gum ducts/cavities differed from that of wound exudates. The occluding material was rich in proteins, lipids, polysaccharides, lignin and phenolics while the material exuded from wounds contained only lipids and proteins. The epithelial cells of the gum ducts showed intense staining for nucleic acids, proteins and insoluble polysaccharides as compared to the neighbouring cells. Some of the epithelial cells accumulated phenolics, which were later released into the duct lumen after dissolution of cell walls. Axial parenchyma cells near the cavities/ducts were free from starch while the vessels were plugged with gum-like material and tyloses. On the other hand, xylem parenchyma cells away from the infection site showed heavy accumulation of starch and negligible amounts of proteins and lipids. The boundary layer was characterised by the presence of few vessels and an abundance of axial and ray parenchyma with heavy accumulation of phenolics, particularly a catacholic type of tannin.

Solid State Fermentation: Comprehensive Tool for Utilization of Lignocellulosic through Biotechnology

Lignocellulosics are widely available natural products which are the tremendous source for the production of enzymes being used for the numerous applications in food, feed, paper, textile and agro-biotechnological industries, ethanol production, bioremediation processes and many more. Enzyme productions from microorganisms are stimulated aggressively through solid state fermentation which meets the demand of getting rid of agro-industrial waste and strengthen the consumption of renewable resources through biotechnology. Though well-developed techniques for enzyme production by submerged fermentation has been found very successful at the industrial sectors; solid state fermentation helps to overcome to the issues of production cost and high yield. Additionally the availability of the substrate with very much economical rate can compensate the overall economic expenses which promote the application of solid state fermentation at industrial level. However several reports regarding fermentation techniques and their pre-treatments are available, the present review will discuss about utilization of lignocellulosics through solid state fermentation for production of enzymes and their enhanced applications in different sectors in recent years.

Morpho-anatomy of Solanum pseudocapsicum

Morpho-anatomical features in leaves, stems and unripe fruits of Solanum pseudocapsicum L., Solanaceae, were investigated by histological methods. Anatomically the plant may be characterised by the presence of uniseriate trichomes, anomocytic stomata, calcium oxalate needles in leaves while presence of oval to circular compound starch grains, angular vessels, vertically upright, uni-biseriate rays and intraxylary phloem with differentiation of internal cambium abutting marginal pith cells and protoxylem in transverse view. Development of distinct internal cambium may be considered as a characteristic feature for S. pseudocapsicum. Intraxylary secondary phloem was composed of sieve tube elements, companion cells and axial parenchyma cells.

Structure And Development Of Internal Phloem In Solanum Pseudocapsicum (Solanaceae)

The development of internal phloem in the Jerusalem cherry, Solanum pseudocapsicum L. (Solanaceae), was studied in young and mature stems. The early presence of primary internal phloem is succeeded by the development of secondary internal phloem from an internal cambium situated between the protoxylem and primary internal phloem. In the second and third visible internodes of the young stem, procambial derivatives begin to differentiate as discrete strands of internal protophloem in a perimedullary position prior to the differentiation of protoxylem and external protophloem. In 6–8 mm diameter stems, sieve elements of the internal phloem become non-conducting, begin to collapse, and undergo obliteration. In 15–20 mm diameter stems internal cambium is initiated from the parenchyma cells situated between the protoxylem and primary internal phloem. The development of internal phloem and an internal cambium in S. pseudocapsicum is compared with that in other taxa. There seems to be a gradual variation in the origin of an internal cambium from either remnants of the procambium or dedifferentiation of peripheral pith cells across dicotyledons with an internal cambium.

Evaluation of Schizophyllum commune Fr. potential for biodegradation of lignin: A light microscopic analysis

Abstract Lignin biodegradation potential of Schizophyllum commune Fr. is studied by using sound wood blocks of Ailanthus excelsa, Azadirachta indica, Tectona grandis, Eucalyptus sp. and Leucaena leucocephala. Initially, in vitro wood decay test showed minor weight loss, but it became rapid after one month. After 120 days of incubation, weight loss was minimum in T. grandis (24.05%) whereas it was maximum in A. excelsa (34.44%). Treated test blocks were characterised by enlargement of pits on ray cell wall, formation of additional boreholes in rays, separation of fibres and cell wall thinning and formation of ‘U’-shape notches. Fungal hyphae moved through the xylem cell lumen, and intercellular spaces formed in response to separation of fibres. Hyphae traverse in adjacent cell through the cell wall pits or by making additional boreholes. In all the species studied, xylem fibres and parenchyma (axial and ray) cells were more susceptible while vessels were resistant to fungal attack. In advanced stage of decay, fibres and axial parenchyma lost their rigidity while vessel walls showed uneven thinning. In the tension wood, G-fibres remained unaffected initially but loosening and separation of gelatinous layer facilitated fungal action and showed similar pattern of cell wall deterioration. Among the wood of different species studied, Tectona was more resistant whereas Ailanthus was more susceptible to fungal attack.

The Delignification Pattern of Ailanthus excelsa Wood by Inonotus hispidus (Bull.: Fr.) P. Karst.

In vitro laboratory decay tests on Ailanthus excelsa Roxb. wood revealed that I. hispidus exhibits a combination of both white-rot and soft-rot patterns of wood decay. Early stages of wood decay showed dissolution of the middle lamella as well as defibration and localized delignification of fiber walls; vessels, axial, and ray parenchyma remained unaltered. Delignification commenced from the middle lamellae at the cell corners without any marked effect on the primary and secondary wall layers. In later stages of growth, the species produces typical soft-rot decay pattern by forming erosion channels through the S2 layers of fiber walls, transverse bore holes in the cell walls, and erosion channels alongside/following the orientation of cellulose microfibrils. The rays showed signs of cell wall alterations only after the extensive damage to the fiber walls. After 120 days of incubation, the vessels also showed localized delignification, the erosion of pits, and separation from associated xylem elements. The extensive weight losses under natural and in vitro decayed wood as well as the very soft nature of severely degraded wood indicate that I. hispidus alters wood strength and stiffness.

Anatomical Characterisation and In Vitro Laboratory Decay Test of Different Woods Decayed by Xylaria hypoxylon

Different species of Xylaria are often reported as an endophyte in different groups of plants starting from liverworts to angiosperms. In the present study, Xylaria hypoxylon isolated from branch stubs of living trees was utilised for in vitro decay test to investigate the pattern of cell wall alterations in sound wood blocks of Azadirachta indica, Leucaena leucocephala, and Tectona grandis. Naturally infected as well as in vitro decayed wood showed cavities and erosion troughs at the lumen surface. In laboratory decay test, vertical invasion of mycelia occurred through the lateral wall pits of the vessels and vessel-associated parenchyma while ray cells enabled radial movement of mycelia. At the end of 60 days, the progression of degradation in the fibre cell wall was evident by the formation of transverse boreholes in the cell walls, erosion troughs at the lumen surface, and larger cavities in the S2 layer of secondary wall. The erosion channels were angular to round (i.e. V-shaped or U-shaped). Fungus was also tested for polyphenol oxidase (Bavandemm’s test) production by on-plate assay and was found to be positive. Confocal microscopy revealed delignification pattern during degradation of cell wall of different cell types in all the three woody species. The SEM analysis of degraded wood showed the ultrastructural changes in the cell wall particularly penetration of hyphae through the S2 layer of the cell walls forming tunnels through it.

Histological changes in the cell wall structure during wood decay by Trametes hirsuta and Trametes versicolor in neem (Azadirachta Indica A. Juss)

ABSTRACT Structural alterations in the wood cell walls of neem inoculated with by Trametes hirsuta and T. versicolor were studied by microscopic methods. In vitro decayed wood showed extensive weight loss of test blocks (26.7 and 41.38% by T. versicolor and T. hirsuta, respectively) at the end of 3 months. Selective delignification in the initial phase followed by simultaneous removal of lignin was evident in test blocks inoculated with both the species. The separation of middle lamellae and patches of cellulosic polysaccharides stained blue with Astra blue in the delignified region of the fiber wall during early stages indicates selective mode of decay. In contrast, the occurrence of erosion troughs with characteristic U-notch in tangential sections is a characteristic feature of simultaneous rot that was apparent after 3 months of incubation. The decay pattern occurred concomitantly in all the xylem elements irrespective of general resistance pattern shown by vessel and axial parenchyma cells. At an advance stage, both species of Trametes showed formation of erosion channels along the microfibrils angle of cellulose which is considered as characteristics of soft rot decay type. The sharing of white rot and soft rot decay pattern by both the fungi suggest a phylogenetic link between both groups of fungi.