RESUMO
Taking straws of corn, wheat, and millet as raw materials, we pretreated them with alkaline hydrogen peroxide, and then hydrolyzed by cellulase and xylanase. We selected the total sugar content in the hydrolysate as the indicator to evaluate the hydrolysis of the straws from three crop species, and further optimized the conditions. Then, the hydrolysates of three types of crop straws were used as carbon source for Chlorella sorokiniana culture to assess their effects on microalgal cultivation. The results showed that the optimal hydrolysis conditions for the three crop straws were identified as solid-liquid ratio of 1:15, temperature of 30 â, and treatment time of 12 h. Under such optimal condition, the total sugar contents increased up to 1.677, 1.412, and 1.211 g·L-1 in the corn, millet and wheat straw hydrolysate, respectively. The hydrolysates from the three crop straw could significantly increase both algal biomass and lipid content of C. sorokiniana. Corn straw hydrolysate had the best effect, with high levels of algal biomass (1.801 g·L-1) and lipid content (30.1%). Therefore, we concluded that crop straw hydrolysates as carbon source could significantly promote microalgal biomass and lipid enrichment. The results could lay the foundation for the efficient conversion and utilization of straw lignocellulose raw materials, provide new knowledge for the resource utilization of agricultural wastes, as well as the theoretical basis for the efficient cultivation of microalgae using crop straw hydrolysates.
Assuntos
Chlorella , Hidrólise , Lipídeos , Carbono , Açúcares , BiomassaRESUMO
We isolated bacteria from the phycosphere of Scenedesmus obliques and sequenced 16S rDNAs to establish algae-bacterial co-culture systems. Further, we examined effects of the bacteria on algal growth, and parameters associated with physio-biochemical and oil-producing characteristics of S. obliquus. Seven bacterial strains were isolated, including Micrococcus (strains 1-1, 1-2 and 1-3), Pseudomonas sp. (strains 2-1 and 2-2), Exiguobacterium (strain-3) and Staphylococcus sp. (strain-4). Among them, two bacteria (strain 1-2 and strain 2-1) were characterized as the dominant growth-promoting bacterial strains, which significantly increased algal growth, pigment production, and oil enrichment. After eight days cultivation under microalgal-bacterial (strain 1-2) symbiotic systemat at an initial ratio of 1:10, biomass of S. obliquus was 4.27 g·L-1, about 46.0% higher than that of the control. The contents of chlorophyll a, chlorophyll b and carotenoids were increased by 12.1%, 16.7% and 25.0%, respectively. Oil content was increased by 14.0% and reached to 25.7%, and the oleic acid content was significantly higher than that of the control and up to 16.4%. When co-cultured with Pseudomonas sp. (strain 2-1) for eight days at an initial ratio of 1:5, algal biomass, chlorophyll a, chlorophyll b and carotenoids contents were higher than that of the control by 47.9%, 16.0%, 17.5% and 19.9%, respectively. The total oil (27.1%) and oleic acid (18.2%) contents were increased by 20.4% and 64.0%, respectively. We concluded that Micrococcus (strain 1-2) and Pseudomonas sp. (strain 2-1) could significantly promote algal growth and increase oil production by their beneficial interaction with S. obliques, which could be potentially used in commercial production of S. obliques.