A Data-Driven Approach to Trip Generation Modeling for Urban Residents and Non-local Travelers
Authors: Yang, Fan; Li, Linchao; Ding, Fan; Tan, Huachun; Ran, Bin
Trip generation modeling is essential in transportation planning activities. Previous modeling methods that depend on traditional data collection methods are inefficient and expensive. This paper proposed a novel data-driven trip generation modeling method for urban residents and non-local travelers utilizing location-based social network (LBSN) data and cellular phone data and conducted a case study in Nanjing, China. First, the point of interest (POI) data of the LBSN were classified into various categories by the service type, then, four features of each category including the number of users, number of POIs, number of check-ins, and number of photos were aggregated by traffic analysis zones to be used as explanatory variables for the trip generation models. We used a random tree regression method to select the most important features as the model inputs, and the trip models were established based on the ordinary least square model. Then, an exploratory approach was used to test the performance of each combination of the variables with various test methods to identify the best model for residents' and travelers' trip generation functions. The results suggest land use compositions have significant impact on trip generations, and the trip generation patterns are different between urban residents and non-local travelers.
Cloning and Overexpression of theToyCluster for Titer Improvement of Toyocamycin inStreptomyces diastatochromogenes
FRONTIERS IN MICROBIOLOGY
Authors: Ma, Zheng; Hu, Yefeng; Liao, Zhijun; Xu, Jie; Xu, Xianhao; Bechthold, Andreas; Yu, Xiaoping
The nucleoside antibiotic toyocamycin (TM) is a potential fungicide that can control plant diseases, and it has become an attractive target for research.Streptomyces diastatochromogenes1628, a TM-producing strain, was isolated by our laboratory and was considered to be a potent industrial producer of TM. Recently, the putative TM biosynthetic gene cluster (toycluster) inS. diastatochromogenes1628 was found by genome sequencing. In this study, the role oftoycluster for TM biosynthesis inS. diastatochromogenes1628 was investigated by heterologous expression, deletion, and complementation. The extract of the recombinant strainS. albusJ1074-TC harboring a copy oftoycluster produced TM as shown by HPLC analysis. The Delta cluster mutant completely lost its ability to produce TM. TM production in the complemented strain was restored to a level comparable to that of the wild-type strain. These results confirmed that thetoycluster is responsible for TM biosynthesis. Moreover, the introduction of an extra copy of thetoycluster intoS. diastatochromogenes1628 led to onefold increase in TM production (312.9 mg/l vs. 152.1 mg/l) as well as the transcription of alltoygenes. Thetoygene cluster was engineered in which the native promoter oftoyAgene,toyMgene,toyBDoperon, andtoyEIoperon was, respectively, replaced bypermE*or SPL57. To further improve TM production, the engineeredtoygene cluster was, respectively, introduced and overexpressed inS. diastatochromogenes1628 to generate recombinant strainsS. diastatochromogenes1628-EC and 1628-SC. After 84 h,S. diastatochromogenes1628-EC and 1628-SC produced 456.5 mg/l and 638.9 mg/l TM, respectively, which is an increase of 2- and 3.2-fold compared with the wild-type strain.