Screening Of Mannitol-utilizing Bacteria And Its Application For Treating Waste Water From Brown Algae Processing

The brown algae processing industry is one of the main pillar industries of aquatic products processing in China.Salted kelp and salted wakame are important parts for brown algae processing.In recent years,the processing capacity of salted kelp and salted wakame has increased gradually.The heated sea water for blanching used recycly in the processing,and the organic matter such as mannitol is then continuously enriched,resulting high concentration of organic matter in the wastewater.It will cause serious pollution to the marine environment if directly discharged.In this paper,mannitol was taken as the sole carbon source,the seawater,sea sand,factory discharge sewage,sewage sludge and Pikou(located in north part of Dalian)sea mud were used as sources for screening the microorganisms.Mannitol removal rate and bacterial biomass were used as indicators.The microorganisms were screened,isolated,purified and identified.The strains,which named as sh-2,sh-6,w-1,sh-13,w-6,n-12,sh-0 and sn-1 were isolated and purified,in which sh-2,sh-6,w-1 were identified as Metschnikowia bicuspidata,and the sh-13 strain was identified as Rhodotorula mucilaginosa,w-6 was Sphingomonas,n-12 was Cobetia,sh-0 was Meyerozyma guilliermondii,and sn-1 was Pseudoalteromonas.Those 8 strains were applied to treat the wakame blanching wastewater and kelp blanching wastewater respectively.The strain culture conditions were optimized when taking the COD removal rate as indicator and the optimized culturing time were determined by the results shown on the 72 h culturing curve.The optimal culture conditions of each strain were selected based on the results of single factor and orthogonal experiments.The strains w-1,w-6,sh-6,sh-13,n-12 were selected and optimized for treating wakame wastewater.The COD removal rate of strain w-6 reached the maximum value of 88.68% at 48 h,and the temperature was 28 ° C,the inoculum amount was 10%,and the rotation speed was 150 r/min.The five strains of w-1,sh-13,n-12,sh-0,sn-1 were used in kelp wastewater treatment and optimized,and the strain of sn-1 obtained highest COD removal rate of 84.58% after 60 hours of culture.Its optimum conditions were 28 °C,and the inoculum was 8%.The strain combination of sh-2,sh-6 and n-12 were the best for treating the wakame waste sea water,their COD removal rate was the largest,of 86.24%.For treating kelp waste sea water,the combination of sh-0,w-1 was chosen,their COD removal rate was 85.98%.This experiment is the first time to use the microbial method to treat the waste sea water from brown algae processing,and had made achievements.It is the first application of mixed bacteria combination treatment,which provided an important basis for the practical engineering application of the sea wastewater treatment for brown algae processing.The solution will vigorously promote the sustainable development of the brown seaweedprocessing industry and has very realistic production significance.