| Corn stover is rich in crude fiber,total sugar,and contains a small amount of protein.It is a renewable resource with huge output.However,such resources have not been rationally used and most of them have been burned,which not only wastes resources but also pollutes the environment.Photosynthetic Bacteria(PSB)has high protein content,low nutritional requirements,and can grow in various ways,such as fermentation,protection from light and aerobic,and has the potential to produce single-cell protein feed.To transform corn stover into feed,this article mainly carried out complex mutagenesis and cell fusion biotechnology treatment of Rhodopseudomonas palustris,Rhodopseudomonas sphaeroides and Rhodopseudomonas capsulata,fermentation optimization and breeding the study.In order to obtain photosynthetic bacteria with excellent performance and convert straw into protein feed,this can not only effectively improve the utilization value of corn straw,but also effectively alleviate the environmental pollution caused by burning corn straw.Compound mutagenesis was carried out using 1.5% W / W(the mass concentration is not indicated in the text)ethyl methanesulfonate and 4min ultraviolet irradiation time as the mutagenesis conditions,and a mutant strain was obtained named FJM.After the second inoculation,the utilization rate of phenol and xylose was 97.73% and 94.44% for 72 hours after inoculation with this strain.Through a single factor experiment,the inoculation volume,time,temperature,shaker speed,bed thickness,and material-to-water ratio of FJM fermented corn stover were optimized.On this basis,orthogonal experiments were used to further optimize the fermentation parameters,and the final determination was that the thickness of the lagoon layer was 4.5 cm,the inoculation amount was 8%(v/v),the feed water ratio was 1:10(straw g / distilled water g),and the shaker speed 120 rpm,temperature 31 ?,fermentation for 6 days,the best effect,true protein increased from 4.12% to 23.87%,crude fiber from 37.53% to 14.37%,crude fat from 4.43% to 6.51%,crude ash from 4.0 % Is reduced to 3.51%,and the moisture content of the fermented dried grain is 9.97%.Protoplasts were fused with Candida shehatae and Rhodopseudomonas margarita under Ca2+ concentration of 30 mmol / L,PEG concentration of 35%,fusion time of 15 min,and temperature of 20 ?.One fusion was named RZZ.After 10 consecutive passages,the utilization rate of 4 g / L xylose for 24 hours of inoculation was 86.04%,which was 196.84% and 10.59% higher than those of Rhodopseudomonas palustris and Candida xihatata,respectively.According to the Plackett-Burman method,screen the temperature,time,inoculation volume,layer thickness,shaker speed,feed-water ratio,and initial pH,which are the seven fermentation influencing factors,with significant effects.On this basis,the response surface method was used to optimize the fermentation parameters.The final determination was at pH 7.0,1:10 water-to-water ratio,4 cm layer,temperature 30 ?,shaker speed 120 r / min,fermentation time 5 d,inoculation The effect is best under 9%(v/v)fermentation.After fermentation,the true protein content was increased from 4.12% to 23.69%,crude fiber was reduced from 37.53% to 14.26%,crude fat was increased from 4.43% to 6.55%,crude ash content was reduced from 4.0% to 3.23%,and the moisture content of fermentation dry grain was 9.59 %.To further reduce the cost of transforming photosynthetic bacteria into corn stalk-made feed,the Trichoderma viride and the modified bacteria FJM and RZZ were mixed and fermented,with the aim of simultaneously reducing crude fiber and increasing crude protein.The results showed that the stepwise fermentation of the corn stalk by the fusion protein RZZ and Trichoderma viride could increase crude protein From 7.65% to 25.37%,true protein from 4.12% to 18.87%,crude fat from 4.69% to 5.89%,ash content from 4.06% to 3.85%,fermentation moisture content of 9.97%.The fermentation lees are dried at 40 ?—45 ? to make pellet feed and vacuum packaged.The effective viable bacteria count is 4.83 × 104 cfu / g after storing in a cool and dry place for 30 days.The straw photosynthetic bacteria protein active feed was used as the test group,and Tongwei No.156 feed was used as the control group to study the straw feed aquaculture effect and culture water purification effect.The results showed that the relative growth rate of grass carp in the experimental group was 324.34%,which was 48.78% lower than that in the control group,and the feed coefficient was 1.2%,which was 0.3% lower than that in the control group.However,the survival rate of grass carp was higher than that in the control group(quantity proportion).There was no significant difference in pH and dissolved oxygen in the aquaculture water body.The ammonia nitrogen content in the experimental group decreased from 1.31 mg / L to 0.65 mg / L,and the nitrite content from 0.153 mg / L to 0.115 mg / L.In the control group,the ammonia nitrogen content increased from 1.35 mg / L to 1.55 mg / L,and the nitrite content increased from 0.151 mg / L to 0.160 mg / L.FJM and RZZ can effectively use the degradation products of corn stover for their own growth and reproduction,thereby converting the degradation products of straw into single-cell protein,improving the utilization value of the straw,and achieving the purpose of feeding the straw.The feed produced by the improved bacteria fermented straw can effectively reduce the content of nitrite and ammonia nitrogen in the water quality and improve the survival rate of fish.It can be seen that the use of modified photosynthetic bacteria fermented corn straw to produce high-protein active feed has great potential in fish farming... |
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