Study On Mixotrophism Of Spirulina Platensis By Enzymatic Hydrolysate Of Tilapia By Products

The mixotrophic culture of Spirulina platensis at different addition of Enzymatic Hydrolysate of Tilapia Byproducts (EHTB) was investigated. The effects on the growth, the variation of nitratase metabolism, temperature, light intensity of S.platensis were studied after adding EHTB to Zarrouk medium. The mixotrophic culture of was optimized for the quest of applying Tilapia byproducts in production and new utilization of S.platensis. Main results are as follows:1.The growth of S.platensis in mixotrophic culture were studied after added with EHTB of papain and fishsoluble which form Tilapia byproducts. The results show that when EHTB is appended, the biomass increased 40.4%, the content of chlorophyll increased 35.4%, when fishsoluble is added, the content of chlorophyll increased 21.1%, but not much change with the biomass. In the meantime, both organic substrates were not so obvious effects on the content of phycocyanin. So that EHTB was better than fishsoluble in respect of growth-promoting effects of S.platensis.2.It was found that the growth of S.platensis could be affected by different addition of EHTB.The results showed that adding EHTB 0.5‰⁵.0‰could promote the growth of S.platensis. Compared with the control group, while adding EHTB 3.0‰, biomass, the content of chlorophyll, protein, and nitrate reductase activity (NRA) were the best, and each of them increased 40.4%, 35.4%, 34.3%, 48.7% (the 2nd day), adding EHTB 7.5‰, the growth of S.platensis was inhibited. Furthermore, EHTB would buffer pH of culture medium, but not much change with phycocyanin.3.We investigate that the different temperature between 15℃⁴0℃makes a impact on mixotrophic culture of S.platensis with EHTB, under the light intensity of 450μmol·m^-2·s^-1. The results showed us the following truth, (1) the addition of EHTB between 15℃ 35℃can increase the S.platensis biomass and at 35℃the largest, 38.2%; (2) between 30℃⁴0℃, it's beneficial to accumulate the content of chlorophyll, and at 30℃the highest chlorophyll content,15.4%; (3) the optimum temperature range was widen from 20℃ 35℃to 25℃ 35℃and of which at 30℃ the phycocyanin content was the highest, 15.04%, it also increased the phycocyanin content of S.platensis, at the low temperature 15℃²0℃and at 15℃the most, 15.1%; (4) the increasing of protein content between 15℃ 35℃offsets the negative influence on protein accumulation especially at low temperature4.We investigate that the different light intensity between 180μmol·m^-2·s^-1 720μmol·m^-2·s^-1 brings the different influence of mixotrophic culture of S.platensis with EHTB, at 30℃. The results showed us the following truth. (1) the addition of EHTB will increase the S.platensis biomass between the light intensity 180μmol·m^-2·s^-1540μmol·m^-2·s^-1, and in 450μmol·m^-2·s^-1 the biomass is the highest; (2) it will significantly increased the chlorophyll and protein content between 180μmol·m^-2·s^-1450μmol·m^-2·s^-1, and at 450μmol·m^-2·s^-1 it increases the most of chlorophyll content, 11.7%; (3) in low light intensity 270μmol·m^-2·s^-1 protein content increases significantly, up to 20.0%, but phycocyanin content of S.platensis does not significantly change.5.Under the condition of low temperature and low light intensity, 15℃and 180μmol·m^-2·s^-1, the addition of EHTB can improve S.platensis biomass, chlorophyll content and protein content but makes no significant difference to the phycocyanin content, in which the contents are increased by 33.3%, 10.2%, 16.6% respectively.6.The effects of three substances which are carbon source NaHCO3, nitrogen source NaNO3, phosphorus source K2HPO4 on the biomass of S.platensis and the optimized dosages were studied, it showed that NaHCO3 12.6g/L, NaNO3 1.5g/L, K2HPO4 0.4g/L can demand the three elements of carbon, nitrogen and phosphorus in mixotrophic culture of S.platensis with adding 3.0‰EHTB, so it was economical comparing with traditional Zarrouk medium. Compared with the control group, total content of amino acids increased 27.59%, Mn, Mg, and K all increased in the mineral element, and Mn was the best, and increased 137.17%, the content of protein, biomass, chlorophyll were increased, each of them increased 38.09%, 22.79%, 37.57%, but not much change with phycocyanin.