Single cell oil production by a novel yeast Trichosporon mycotoxinivorans for complete and ecofriendly valorization of paddy straw

Background: Oleaginous yeasts can be grown on different carbon sources, including lignocellulosic hydrolysate containing a mixture of glucose and xylose. However, not all yeast strains can utilize both the sugars for lipogenesis. Therefore, in this study, efforts were made to isolate dual sugar-utilizing oleaginous yeasts from different sources. Results: A total of eleven isolates were obtained, which were screened for their ability to utilize various carbohydrates for lipogenesis. One promising yeast isolate Trichosporon mycotoxinivorans S2 was selected based on its capability to use a mixture of glucose and xylose and produce 44.86 ± 4.03% lipids, as well as its tolerance to fermentation inhibitors. In order to identify an inexpensive source of sugars, nondetoxified paddy straw hydrolysate (saccharified with cellulase), supplemented with 0.05% yeast extract, 0.18% peptone, and 0.04% MgSO4 was used for growth of the yeast, resulting in a yield of 5.17 g L−1 lipids with conversion productivity of 0.06 g L−1 h−1 . Optimization of the levels of yeast extract, peptone, and MgSO4 for maximizing lipid production using Box­Behnken design led to an increase in lipid yield by 41.59%. FAME analysis of single cell oil revealed oleic acid (30.84%), palmitic acid (18.28%), and stearic acid (17.64%) as the major fatty acids. Conclusion: The fatty acid profile illustrates the potential of T. mycotoxinivorans S2 to produce single cell oil as a feedstock for biodiesel. Therefore, the present study also indicated the potential of selected yeast to develop a zero-waste process for the complete valorization of paddy straw hydrolysate without detoxification

Bacterial pretreatment of paddy straw for enhancing biogas production

Aim: Increasing the digestibility of paddy straw and biogas production by pretreating it with bacterial culture, Delftia sp. PP4_S3. Methodology: The chopped (3-5 cm) and soaked paddy straw in different sets (each with 250 g PS) were pretreated with bacterial culture i.e., Delftia sp. PP4_S3 suspension for different durations and was further utilized for biogas production. Results: Biogas yield was highest (180 l kg-1 PS) in paddy straw treated with Delftia sp. PP4_S3 for 3 days showing an increase of 66.1% from untreated paddy straw. Chemical analysis approximately showed that maximum reduction of lignin (45.7%) and silica (17.7%) occurred in 5 days of pretreatment. Interpretation: Treatment of paddy straw with Delftia sp. PP4_S3 enhance the digestibility of paddy straw by lowering the lignin and silica content. These observations showed that Delftia sp. PP4_S3 is a good lignocellulosic degrader and can be efficiently used for enhancing biogas production

Yield, Fruit Body Diameter and Cropping Duration of Oyster Mushroom (Pleurotus sajor caju) Grown on Different Grasses and Paddy Straw as Substrates.

The present experiment aimed at finding the suitability of some grasses as cost effective alternative substrates, for cultivation of one species of oyster mushroom viz., Pleurotus sajor caju (Fr.) Singer in eastern India. Relative efficacy three grasses viz., kash grass (Saccharum spontaneum L.), sabai grass (Eulaliopsis binata C.E. Hubb (Retz.)) and lemon grass (Cymbopogon citrates Stapf.) was tested by using each of them either as whole substrate or in combination with the conventional substrate i.e., paddy straw in 3:1, 1:1, and 1:3 ratios. Results revealed that the maximum yield of mushroom was recorded under paddy straw with biological efficiency of 85.9%. However, no significant difference in yield was found when 25% or 50% of the conventional substrate (paddy straw) was replaced by lemon grass and sabai grass. The results indicated that grasses which are available in plenty in the forests and wastelands of lateritic uplands of eastern India can be utilized successfully as promising substrate for the commercial cultivation of Pleurotus sajor caju.