M.N. Shashirekha

Improvement of the bioconversion and biotransformation efficiencies of the oyster mushroom (Pleurotus sajor-caju) by supplementation of its rice straw substrate with oil seed cakes

Supplementing the rice straw substrate colonized by the mushroom, Pleurotus sajor-caju, withpowdered oil seed cakes (mustard, niger, sunjower, cotton, and soyabean) increased the mushroom yields between 50 and iOO%, compared to the unsupplemented substrate. Oil seed cake supplementation also effected an increase in the solubility of the rice straw substrate; there was an increase in the contents offree sugars and amino acids, and a decrease in cellulo-hemicellulosics. Correspondingly, there was also an increase in the activities of carboxymethylcellulase, hemicellulase, and protease. In vitro dry matter enzymatic digestibility measured by two-step enzymatic digestibility of the spent straw (material remaining from the straw substrate, supplemented with the oil seed cakes), indicated a signt

Enhancement of bioconversion efficiency and chemistry of the mushroom, Pleurotus sajor-caju (Berk and Br.) Sacc. produced on spent rice straw substrate, supplemented with oil seed cakes.

cant increase over that of the spent straw derived from the unsupplemented lot.

Biodegradation of gossypol by the white oyster mushroom, Pleurotus florida, during culturing on rice straw growth substrate, supplemented with cottonseed powder

Abstract The effect of supplementing the spent rice straw substrate, selected at two different levels of bioconversion efficiency (BCE), 8 and 12%, of Pleurotus sajor-caju, with extra organic nitrogen (in the form of oil seed cakes) was studied on further production of mushrooms, their chemistry and the increase in the in vitro dry matter digestibility (IVDMD) of rice straw. The spent rice straw was supplemented with the oil seed cake powders in amounts equivalent to 0.15–0.60% of nitrogen present in the undegraded rice straw, that is used for mushroom culturing. The cotton seed powder proved to be better in enhancing the mushroom yields (up to 12 times those of the unsupplemented spent straw), than the other oil seed cakes such as mustard, niger, soyabean and sunflower. Chemically, the cottonseed powder supplemented mushrooms showed increased protein, fat and decreased carbohydrate contents. Also, there was a significant reduction in the spawnrun period, compared to the unsupplemented rice straw. A considerable increase in the IVDMD of the supplemented spent straw was observed as compared to the IVDMD of the unsupplemented spent straw. Due to cotton seed cake supplementation, there was about a 27% increase in the IVDMD value of the spent straw that resulted in 8% BCE. The mushrooms produced on the spent rice straw substrate, with supplementation of cottonseed powder, did not contain any residues of gossypol, and accordingly, they can be a valuable food or feed.

Starch digestibility and predicted glycemic index in the bread fortified with pomelo (Citrus maxima) fruit segments

The capacity of the white oyster mushroom, Pleurotus florida to biodegrade gossypol was studied, when grown on rice straw supplemented with cottonseed powder. The mushroom fruiting bodies did not contain any residues of gossypol at concentrations of cottonseed powder ≡0.15–0.60% nitrogen contents of rice straw at the end of mycelial ramification. However, the cottonseed supplementation (at 0.30% N level itself) caused a doubling in the mushroom yield and its protein content, per unit weight straw substrate. The mushroom mycelium when grown on synthetic medium in liquid cultures was able to biodegrade gossypol. A pre-incubation period of 5 days before the addition of gossypol into the culture medium, an inoculum load ≡10 mg and an incubation period of 10 days at 25 °C caused the biodegradation of 100 μg gossypol. Increased concentrations of gossypol required increased duration and increased inoculum levels to effect biodegradation. However, the effect was more pronounced with an increase in inoculum density. The fungal monoculture when grown in rice straw (powder) (5%) + glucose (1%) liquid culture medium, showed an increase in hexosamine content and laccase activity that produced an increased degradation of gossypol over an incubation period from 5 to 25 days. Enzymic extracts of the mycelial monoculture raised on the chopped rice straw substrate when incubated with 100 μg of gossypol demonstrated its biodegradability; the increase in enzyme concentration showed enhanced gossypol degradation. This study adds to the world list of organic compounds that Pleurotus is able to biodegrade, and explains the cause of non-yellowing of the white oyster mushroom (P. florida) fruiting bodies, during culture on rice straw with supplementation of cottonseed powder for enhancing the mushroom yields.

Pre-planting Treatment of Seed Potato Tuber Pieces to Break Dormancy, Control Tuber Piece Decay and Improve Yield

The aim of this study was to evaluate the starch digestibility and predicted glycemic index in breads incorporated with pomelo fruit (Citrus maxima) segments. Volume of the white and brown breads supplemented with pomelo fresh segments increased, while the crumb firmness decreased. Bread with 20% fresh and 5% dry pomelo segments were sensorily acceptable. Bioactive components such as phenolics, flavonoids, naringin and carotenoids were retained to a greater extent in bread containing dry pomelo segments. The pomelo incorporated bread had higher levels of resistant starch fractions (3.87-10.96%) with low predicted glycemic index (62.97-53.13%), despite their higher total starch (69.87-75.47%) content compared to control bread. Thus pomelo segments in the product formulations lowered the glycemic index probably by inhibiting carbohydrate hydrolyzing enzyme activity which could be attributed to naringin. Hence fortified bread prepared from pomelo fruit segment is recommended to gain nutritional value and to decrease the risk of diabetes.

Inhibition of growth of the mushroom Pleurotus flabellatus (Berk and Br.) Sacc. on rice straw, by Sclerotium rolfsii Sacc.

In laboratory and field experiments at Mysore, cut pieces of potato cv. Kufri Jyoti tubers were treated with 7 antimicrobial chemicals at a variety of concn to control decay caused by Erwinia carotovora and Fusarium oxysporum. Mercuric chloride was the most effective in controlling decay, followed by streptocycline, Dithane M-45 [mancozeb], ferrous sulphate, Emisan [2-methoxyethylmercury chloride], Bavistin [carbendazim], Oxine [oxine-copper?] and TEM, a trace element mixture. Mercuric chloride was most effective at a concn of 100 mg/litre but the other fungicides gave increasing levels of control up to the highest concn tested (500 mg/litre). Tuber yields ranged from 9.7 kg/plot with mancozeb to 15.6 kg with TEM. In experiments on dormancy breaking in seed tubers stored at 4

Chemical and biochemical changes in the rice straw substrate related to the morphogenesis, cropping patternand yield of Pleurotus florida (Block & Tsao.)

Abstract Sclerotium rolfsii Sacc. is a serious substrate-borne fungal contaminants found while culturing Pleurotus flabellatus (Berk. and Br.) Sacc. on unfermented rice straw on a commercial scale. Depending on the degree of contamination, the loss in mushroom yield ranges from 80% to virtually total crop failure. Differences in the physiology of the two fungi that account for suppresion of growth of Pleurotus by S. rolfsii are described. At each of the temperatures studied, 20, 25, 30 and 32°C, growth rate of S. rolfsii was several fold higher than that of P. flabellatus . The fungal contaminant displayed the capacity to degrade cellulose and hemicellulose, and demonstrated high rates of cellulolytic and hemicellulolytic activities, per unit time incubation of straw, compared with P. flabellatus ; also the substrate was more solubilised by S. rolfsii . While the carboxymethyl cellulose (CMC)-ase and hemicellulase activities of P. flabellatus were inhibited at pH 3.2, S. rolfsii is known to demonstrate significant activities of these enzymes at a pH as low as 2.0. Sclerotium rolfsii characteristically produced high amounts of oxalic acid compared with P. flabellatus .

Fat and fatty acids of Indian edible mushrooms

Summary Growth and yield of Pleurotus florida on rice straw were studied as a function of temperature. At an ambient temperature of 20˚C, a maximum bioconversion efficiency (yield to substrate ratio, both on a dry-weight basis) of 14.5% was recorded. The net yield was observed over 2–3 flushes, with an interflush period of ca. 7.d. Increase in bioconversion efficiency (BCE) decreased left-over spent substrate and increased the loss of growth substrate as CO2 and H2O. An increased solubility of the growth substrate was observed with increase in BCE. In general, increase in sugars, amino acids, and decrease in phenols, cellulose, hemicellulose and lignin were observed; however amino acids decreased at high levels of BCE. Likewise, the decrease in lignin content was not important above a 10% increase in BCE. Flush co-ordinated operation of the degradatory enzymes in the rice straw substrate was studied. Whilst CMC-ase, b-glucosidase, hemicellulase and protease showed a continuous increase over all the flushes, laccase showed a decline only after the first flush, reflecting the possible non-requirement for lignin degradation thereafter. The growth of the fruiting primordium into a mature fruiting body took 72.h was characterized by an active increase in cellulase(s), hemicellulase(s) and, protease in particular. Laccase activity declined. This observation is associated with the requirement for carbohydrates and protein for growth and development of the fruiting bodies. Hexosamine content in the rice straw substrate increased until the end of spawnrun and declined thereafter, in accordance with the fructification.