The rise in global temperature is a direct reflection of the problem of cellulosic pollution. Hence, it was necessary to find cheap, safe and effective ways to convert these cellulosic wastes into useful products. Present manuscript aims to introduce an effective and applicable strategy for safe conversion of the agricultural cellulosic wastes into useable high protein, carbohydrate and lipid biomass. The current study presents a miniature model for converting the cellulosic waste of straw (residues) into a living biomass containing high amounts of pigments, proteins and lipids stored in the alga, Chlorella vulgaris. Two soil microorganisms with a high ability to cellulose degradation were selected, isolated, biochemically and molecularly identified as Aspergillus terreus and Brevibacillus borstelensis. The obtained results, showed the highest recorded sugar productivity of 648.1µg/l on the 8th day of incubation with A. terreus (untreatment straw), and 814 µg/l on the 4th day with B. borstelensis (pretreatment straw). The mixotrophic nutrition of Chlorella vulgaris grown on degraded straw by both organisms showed significant increment (enhancement) in growth, pigment, protein and lipid content compared to those produced by the alga cultivated on the KC nutrient medium. It could be concluded that treated cellulosic wastes can be used as safe mixotrophic nutrition for microalgae to enhance the productivity of biomass and other biochemical parameters.